If I examine this image using the burning question, "What did Final Fantasy X do correctly to avoid causing offense?" the following "answer" can be claimed.  What Final Fantasy X did correctly is that they reduced the elements they wanted to mix to their most basic form (represented here as the pyreflies) and then remixed these essences to build something new.  This doesn't seem like a novel idea in and of itself, but let's take a closer look at the religion of Yevon as an example.

The religion of Yevon is made up of the following [game script excerpts are from Summers (2006)]:

• Teachings/Professed information

  • Yevon is almighty

    • he is credited for many things: "Praise be to Yevon"

    • followers ask Yevon for things, "On to the temple, where we pray for victory!"

    • his teachings should be followed

  • The people are expected to pray to receive salvation

    • "I'm sure you followed the teachings, before the toxin got to you, of course. Go pray at the temple, and all will return in time."

  • Sin was born because the people used machina, 

    • "But you Al Bhed use the forbidden machina! You know what that means? Sin was born because people used machina!"

  • Machines, particularly ones used for war, should not be used 

    • "They say our machina violate the teachings, eh? Nonsense!  These machina have Yevon's approval. Don't mix them up with the forbidden ones, got it?"

  • The people should strive to beat Sin

    • "Sin will be gone once we atone for our past mistakes!"

    • Regarding an attack on Sin, using forbidden machines, "Although it may be sacrilege to Yevon, their intentions are pure."

  • To truly defeat Sin, the people must atone, 

    • "Sin is our punishment for our vanity. And it will not go away until we've atoned."

  • Sin can only be killed by aeons

    • "The Final Summoning. It's the only way to defeat Sin. The only way. With it, we can call the Final Aeon."

  • Summoners must pray at every temple and receive the temple's aeon before reaching Zanarkand

    • "I have to pray to the fayth in every temple in order to earn the Final Aeon."

  • Zanarkand is a holy city where the final aeon awaits.

    • "Don't tell anyone you're from Zanarkand, okay? Yevon says it's a holy place. You might upset someone."

    • " The Fayth of the Final Summoning lies waiting in the far north, to greet summoners that complete their pilgrimage. At the world's edge...in Zanarkand."

  • The fayth are holy supports of the Yevon faith.  

    • "The fayth are people who gave their lives to battle Sin. Yevon took their souls, willingly given from their still-living bodies."

  • The dead should be guided to the Farplane so that they will not become fiends

    • "It is a summoner's sacred duty to send the souls of the departed to the Farplane!"

  • Only summoners are allowed in the chambers of the fayth (the temple's holy place)

    • "The chamber beyond is a sacred place. Only summoners may enter."

  • Only summoners and their guardians are allowed in the cloister of trials (the testing ritual preceding the chamber of fayth)

    • Tidus is pushed on the elevator to Kilika's cloister of trials.  The game won't continue until you meet everyone at the door to the chamber of fayth.  "Only guardians allowed, and I'm sure no guardian. Well, I guess it's too late now."

  • Summoners are chosen,

    • "The summoners are practitioners of a sacred art, sworn to protect the people of Yevon. Only a chosen few become summoners, who call forth entities of greater power: the aeons. The aeons hear our prayers and come down to us. They are the blessing of Yevon."

  • Requires that followers consider themselves children of Yevon, or Yevonites

    • Those who oppose the religion are called heathens and traitors and are thus exiled as was Yuna

• Behind the Scenes (founding) information   

  • At the time of the machina war, Zanarkand was a city of summoners who used machina for pleasure and Bevelle was a city of machina who used machina for war

  • Yevon summons Sin

  • Yevon is no longer human

  • Zanarkand was the first city Sin destroyed when Yevon lost his humanness

  • Zanarkand is where Yunalesca created the first final aeon, and is where she waits to create this same weapon for future summoners

  • Yunalesca provided the teachings that founded the church

  • Sin is never ending, but the world of Final Fantasy X must not be made aware of this

  • The unsent of a select few (Yunalesca primarily, and Mika secondarily) are necessary for the world to maintain hope of peace

  • Sin was born to protect the dreaming fayth on Mount Gagazet, and, as part of this, was commanded to destroy places with large populations or high dependence on machina.

As has been discussed in other parts of this mystory, this religion has strong associations with Catholicism; however, a number view this game as anti-organized religion instead of anti-Catholic.  I think that SquareEnix needed to create this illusion so that the game could sell. This, in turn, may give my theory about how they achieved this some ghostly legs to stand on.  I believe that they achieved this illusion by first breaking down Catholicism to its barest bones (or pyreflies).  The pyreflies regarding appearance (clothing, names, architecture, etc.) were set aside for later mixing.  The ones that remained were matched with elements from other religions (even if some matches were loose).

The below list is of principles that a sample of religions have in common with and may have inspired the Yevon religion

• Multiple religions

  • people should strive to be good

    • the world of Final Fantasy X must strive for atonement

• Pre-Christ Judaism (according to the old testament Bible)

  • God is almighty (Genesis 35:11)

    • Yevon is almighty

  • A single act (eating forbidden fruit) allowed sin to enter the world (Genesis 3:14-24)

    • Sin is said to have been born by the use of forbidden machina.

  • routine sacrifices had to be made to atone for sins (Leviticus 1-6)

    • routinely summoners were sacrificed

  • only priests were allowed to enter the most holy place of the temple (Numbers 18)

    • only summoners could enter the chamber of fayth

  • eating certain animals made you unclean (Leviticus 11)

    • use of machina was taboo

  • requires that the laws in scriptures be followed (Psalm 1:1-6)

    • believers of Yevon ran the government and marked anyone who doesn't follow the teachings of Yevon a traitor

  • require only Judaism be followed (Exodus 34:14) 

    • it is thought that only the teachings of Yevon could save the world of Final Fantasy X

  • ​afterlife consists of heaven and hell (Daniel 12:2)

    • there is an afterlife called the Farplane which is beautiful and suggests a heavenly state

  • the guidance of priests are needed for salvation (Leviticus)

    • summoners are needed to guide dead souls to the Farplane

• Christianity/Catholicism (according to earlier research for this project and the Bible)

  • God is almighty (Genesis 35:11)

    • Yevon is almighty

  • beneath God/Jesus, Mary is the most holy (Conover, 2008, p.226)

    • Yunalesca, below Yevon, is most worshiped

  • saints are the most holy of men and can be called upon to intercede to God (Woodward, 1996)

    • fayth and summoners are called upon to face Sin

  • people are inherently evil (Romans 5:12)

    • the world of Final Fantasy X must atone for its sins

  • requires prayer to God (Luke 18:1)

    • the people must pray at the temples

  • requires that the teachings of the Bible be followed (Exodus 34:14)

    • Teachings of Yevon must be followed

  • afterlife consists of heaven and hell (Mark 9:42; Romans 2:6-8)

    • there is an afterlife called the Farplane which is beautiful and suggests a heavenly state

  • requires belief in Jesus for salvation (John 11:26)

    • requires that the world of Final Fantasy X put its hope in its summoners

  • dying for the sake of the faith is good (Matthew 16:24-25)

    • summoners and fayth die for the sake of defeating Sin

• Shintoism (according to Naofusa, 2006, "Shintoism," 2012, "Shinto At A Glance," 2011, and Shinto Online Network Association, 2006) 

  • no explanation of world creation

    • the world of Final Fantasy X has no world creation story

  • to quote Disney's Pocahontas, "Every rock and tree and creature has a life, has a spirit, has a name."

    • which might help explain how pyreflies make or assist in making so many forms of life

  • worship largely takes place at shrines

    • worship largely takes place in temples

  • religion based on rituals

    • prayers, and sendings

  • identity is based on ritual (you follow Shinto because you partake in ritual)

    • in the world of Final Fantasy X you pray and don't use machina

  • rituals are often purifying or exorcising in nature with the exception of life passage ceremonies such as weddings

    • sending and prayers are often purifying in nature

  • primarily localized religion (deities are spread all over Japan and different deities are worshiped in different ways)

    • each temple has a different aeon

  • shrines (at least to begin with were)/are not open to humans

    • the cloister of trials and chamber of fayth are not open to just anyone

  • has ethical principles but no commandments

    • Yevon does not teach morality

  • no afterlife

    • the Farplane (as it is experienced in Guadosalam) is not a place where the spirits of the dead roam

• Buddhism (according to "Buddhism," "A Basic Buddhism Guide: Introduction to Buddhism," and "Buddhism At A Glance," 2009)

  • no explanation of world creation

    • the world of Final Fantasy X has no world creation story

  • focus on personal spiritual development

    • the world of Final Fantasy X must atone for its sins

  • goal is to achieve nirvana

    • may explain why Farplane is only place of afterlife

    • the rare chance of achieving nirvana is similar to Yunalesca's point that the world of Final Fantasy X has little (if any) hope of achieving such purity

  • no belief in personal god

    • Yevon is not called a god

    • followers do not have personal connections to Yevon

  • "life is both endless and subject to impermanence, suffering and uncertainty" ("Buddhism At A Glance," 2009)

    • the latter three might be connected to the effects Sin has on the world of Final Fantasy X.  Sin changes with each defeat, Sin causes suffering, the eternality of Sin's defeat is uncertain prior to Yuna's defeat of Sin.

  • "change is always possible" ("Buddhism At A Glance," 2009)

    • Sin could be defeated some day

  • people are reincarnated

    • may explain why pyreflies take so many forms

  • impermanence: nothing "lasts forever.  Our mistaken belief that things can last is a chief cause of suffering," ("Buddhism At A Glance," 2009)

    • may speak to why the world leaders have accepted the certainty of death

  • our sense of self comes from "temporary mental processes and events" ("A Basic Buddhism Guide: Introduction to Buddhism")

    • may contribute to pyrefly qualities

  • requires meditation

    • requires prayers

  • Ego 

    • as described by "A Basic Buddhism Guide: Introduction to Buddhism," Ego could be part of what inspired Sin

  • The cycle of rebirth

    • as described by PBS's "Buddhism," may inspire what causes the dead to become fiends instead of spirits on the Farplane

• Confucianism (according to "Confucianism") 

  • ritual based

    • prayers and abstinance from machina mark Yevon following

  • no afterlife preached

    • the Farplane is the only afterlife

  • one should be loyal to the state

    • anyone that does not follow the teachings of Yevon are traitors

• Hinduism (according to "Hinduism At A Glance," (2009) "Fast Facts on Hinduism," and "Nine Beliefs of Hinduism")

  • people are reincarnated

    • may explain why pyreflies take so many forms

  • people can be freed from cycle of incarnation

    • the world of Final Fantasy X can be freed of Sin

  • ​the guidance of gurus are needed for salvation

    • summoners must guide souls of the dead to the Farplane

  • there is a supreme god

    • Yevon is almighty

  • worship held in temples and home shrines

    • worship is held in temples

  • all life is considered sacred

    • this is why fiends are fought and summoners are valued

With the religious principles connected, the remixing began, and SquareEnix added some of its own beliefs into the mix.  Once the founding principles were decided upon, then the appearances were remixed and constructed into a new form.