I'll put my comments inline
Here is a rough draft of what could be pantheon changes. The general logic is the pantheon should help address weaknesses (like giving food to a low food start) while making sure the gameplan makes sense.
Earth Mother:
2
1
to monuments, 1
to mines on improved resources.
Logic: Most mines don't give food, which makes working several in a city really difficult. This is good in a capital with 3 mines, but its awkward when after a settler is built you need to work food tiles instead of those mines. Food everywhere helps.
--Seems reasonable, I would give this a go.
Ancestor Worship:
1
2
to councils. 1
per 4
in a city.
Logic: Less culture but slightly more faith. This is high faith and really easy to use, it's a good backup option.
--I think its easy to underestimate how much of a nerf this is, but its probably warranted. Like you said, it becomes the ultimate "plan B", I never want this as my main, but if my terrain just doesn't fit with other pantheons its always an option.
Sun God:
1
2
to wheat, rice, and corn. 2
to granaries.
Logic: The only version of this was bad. It gave food to land that already had really high food.
Here, it gives what those cities often lack, hammers and gold. The bonus is applied to resources themselves, not a farm, because workers need to be improving luxuries at this stage. The yields are high because there is no farm luxury, so you usually get fewer of these than you do camps/whatever.
This is very high faith which means it could be worth considering even with no culture.
--I think the instant yields are what sells this. Its total bonuses still aren't all that amazing, but combined with the fact they come online immediately if you get that nice 2-3 wheat city is a big deal, and I agree it should be faith heavy on terrain that I would consider sun god on. I'm game.
Ok so the other one on the block was Commerce. Lets dig into some ideas:
Commerce V1 (more heavily focused on the trade aspect)
Trade Units build 50% faster (this is a big deal in the early game, TRs are quite pricey)
4
for every TR
+3 Great Merchant GPP in capital
Commerce V2 (WLTKD are another common aspect of merchant play, so a focus on that).
+5% growth during WLTKD
2
for every TR, in the capital, and in each connected city (aka this kicks in before the 2nd city is made).
+3 Great Merchant GPP in capital
Commerce V3 (Markets are the definitive building for early commerce. While it does exist on renewal, its a niche enough building that there is no reason you can't have 2 pantheons that give it a boost).
+1 culture, faith, and science on Market
2
for every TR
+2 Great Merchant GPP in capital