Being able to kill god is a pretty common element of many different video games, so i wouldn't be surprised if it makes its way into DF.
My question was mostly about people being able to create a new god by believing. Or changing god's aspects like sphere by believeing. For example a new religion with slightly different view of the god emerges and becomes dominant in the world will the corresponding god change to fit the religion?
As far as I understand, just about anything that's reasonable is desired to be possible.
Real world religions have changed over time, with the pantheon members shifting as the stories about them change (and they've been adopted/taken over by new regimes, such as the Greek pantheon sort of being transformed when the Romans created their pantheon).
The Abrahamic religion branching is an ongoing example of real world religion diversification from a sort of common root ("ongoing" in that new versions pop up over time, claiming to be refinements or the "truth" over whatever they derived from, usually with the "parent" outright rejecting these "children" as just new heretic sects).
In a world where gods actually exist and have agency there may be a need for gods to be able to split (e.g. Zeus spawning a Jupiter that may exist in parallel if the source pantheon remains active in some parts of the world).
The worshiper base affecting the gods is definitely a reasonable case that's been present in fiction.