A player who knows how to optimise would likely become better that the statted gods, in this case you could boost the abilities of your NPC gods to match your players, .
Now the question if players should be able to become gods, it really depends on your desires, do you want as a group to play an immortal-deific game?
If yes then the rules in Immortal Handbook are really helpful to make characters and NPCs that are immortal.
It really is a try and see what works since a lot will depend on how good are your players at optimising your characters and samewise your own ability to counter them.
Now the question if players should be able to become gods, it really depends on your desires, do you want as a group to play an immortal-deific game?
If yes then the rules in Immortal Handbook are really helpful to make characters and NPCs that are immortal.
It really is a try and see what works since a lot will depend on how good are your players at optimising your characters and samewise your own ability to counter them.