These are all interesting ideas.
Heroes could be a god-player thing - a way to interact with the world while they slumber and give boons to civs they like. In return, make gods far less powerful. Creating artifacts should take more FP, while zaps & random mutations might still be low-cost. Supernerd suggested good idea of weather. Also, gods could be showing mortals what there already is on the nearby tile (a ray from heavens fell near your settlement, with cache of spears lying where it landed. Praise ...!)
I kinda liked how Neheb survived everything through discipline. I'm pretty sure this disciplined tenacity of cobra style is going to survive whatever the world throws at the,
The thing is, I'm not expecting the gods to be slumbering for all that long. The problem with making the gods less powerful is I know from experience that it can be boring for a god to spend ten turns in a row unable to do anything because of lack of FP. I know that still happened sometimes in this game, but I tried to make it less likely.
Maybe make it so that the basic landscape cannot be changed anymore, but the climate can be.
Interesting idea. Maybe Amastay's purification blast had the effect of locking the tiles in place. I'll give it some thought.
Maybe we could make it so anyone can play a hero in addition to playing their god or their civ, and if someone wanted to join and play just a hero, they could. I'm not sure how heroes would arise, though. Randomly? Like legendary workers did in the stone age? If heroes are rare, would that mean that people will get mad over who gets to control them? Maybe I should just scrap this idea of heroes altogether.