Personally I would like it if you could spend favor to add extra gods into the Pantheon at the cost of going less deep into the current Gods powers. A wide vs tall decision.
Well, that's part of the problem. Favor allocation is automatic, and it'd be good for AI reasons to keep it that way; adding more gods into your pantheon AUTOMATICALLY slows the growth by forcing the Battle and Building favor to be split one extra way, but there's no built-in way to make that tall-vs-wide decision.
But in terms of adding extra gods, I see it like Culture: you accumulate it, and when you hit a threshold, POOF, extra policy/god. No actual "spending" involved, just a decision to be made every once in a while. I was looking at aiming the balance to where you'd get minor god #1 on turn ~50, #2 on turn ~125, #3 on ~200, and #4 on ~300. (Obviously there's plenty of wiggle room there.) So the question is whether I should speed that up a bit, but give the player (and AI) ways to slow it down by buying Myth units or Heroes. Originally, I was going to have all myth units and heroes work this way, but between the religious buildings and the Events, I don't think I need to; as long as you can get Heroes fairly often through Events, it's better for AI reasons to make that be the only way.
By making it automatic, the only thing the AI has to worry about is which god to add or which answer to pick on the Events. And for that, even a simple random choice would work pretty well.
As for favor levels, I think they go on a separate page.
The issue I'm having here is a mechanical one: I need to put TopPanel.lua in the Base mod, because the Ascension mod needs access to it as well for a Neutronium issue. So while I can put Mythology-specific stuff in that panel (and I have) by sticking it inside an IF that only triggers if the Mythology mod is active, I've got only limited access to the Mythology-related game databases (including the Favor total). Which means I'm looking at having information be spread around three or four pages, and that starts to get awkward if I pile on even more windows.
I envision the religion screens being the one presented, then a second one that displays your current Pantheon selections, and the favor levels and unlocked powers of each god.
Slight issue: you don't unlock powers per god. You unlock powers per Focus, and it's handled per city (so when you unlock the level 3 buildings, it doesn't immediately move every city to level 3). The fact that the level 4 building can only be reached in your capital makes it a good benchmark, but it's not quite the same thing. Hence the comments about a detailed Favor status page. Sort of like the Great Person page, something that shows how close each city is to upgrading each Focus. (Actually, VERY similar to that Great Person page.) Clicking on a focus should show you what the level 1, 2, 3, and 4 buildings can do, but I can handle that through a simple tooltip easily enough. Or more specifically, through the four info tooltips for the four buildings. Like how mousing over a building icon in the Tech Tree shows you the building's Help page.
I was thinking of makign that screen have a unique background based on religious type.
I had the same idea, but I was putting most of the artistic flourishes on the back burner until I got more of the mechanics in place.