well, how Atlus missed completely the golden occasion of doing a SMT or Persona centered on Mayan (or precolombian in general) mythology escapes me (2012 and all that....) but in general, I think that the balance between "local" and "exotic" mythology is essential (please note is bilateral: western mythology is exotic in Oriental eyes and visa-versa: to Japanese eyes Thor or Gabriel appear exotic as in our eyes Susano-o or Amaterasu are exotic...)
Your starting Persona is Wart which will evolve into Arthur.
We actually have a P5 board for this btw.
I also think that a Christian theme would be cool, but with the bad guys having the holy angels, Gabriel, Raphael, etc and the good guys having the fallen angels and Inferno's demons. The final persona for the main character could be a whole new redesing of Lucifer. .
They already did. It's called Shin Megami Tensei.
Here, have a video of the protagonist fighting GOD: http://www.youtube.com/watch?v=sFntNMe5ic8 --- Action speaks louder than words. But words, when used right, overwhelm any action - Me, 2006 Let's put a smile on that face - The Joker, 2008