Hi! That is not currently possible, but I was experimenting with a mode for just that linear type of progression. I didn't love it :) But maybe some day.
TThanks for the answer!! I was running some simulations, and I noticed that after a while (100 years, maybe) empires attacks less each other, because one religion ends up dominating the map, and empires gain a huge boost in relationship for sharing the same religion. One solution would it be to forbid peace and alliances, but I kind of like them, it gives the smaller empires a chance to unite against the bigger ones. Is there a way to change religions parameters in sanbox mode?