I might have problems with this story
coming around full circle (ex. Keiichi comes back to life in the
end and all is back to normal) without there existing some lasting
consequences for the players, and I'm not talking about the
emotional impact either. Someone has to pay a price or give up
something in exchange for a de facto status quo (I won't mention
the possibility of any goddess, Bell in particular, losing their
powers, I think I've seen that in another fic somewhere *bg*).
That is, of course, if you're going to go in that direction.
Actually, if Keiichi just died in a normal, mundane manner, there wouldn't
be much reason for a big quest to return him to life (unless there was
another plot point that created this reason). He was a good enough person
to deserve a wish in the first place, and behaved very nobly afterwards -
that means he's going straight to Heaven (which is a very real place in
AMG :)). All Bell would have to do to stay beside him would accompany him
there, which she can do easily.
Of course, that strangely neutral magical energy that surrounded Keiichi
upon his death is probably our reason for a big quest, but even so it
might all end with Keiichi just going to Heaven instead of ressurrecting.