The Tavern

Some divine-favoured race, effectively antiDemigod. Whatever name and more precise favour.
Features:

Decently bad aptitudes (like -1 everything).
High invocations (+4!).
You get apt bonus, which depends on your current god (effectively you have okayish apts for god-favoured skills).
Increased piety gain.
Decreased god change penalty (may be even negated, may be aslo keep some piety or keep some piety if you come back to god).
Neutral hp/mp/stats.

Examples of apt bonus:

Oka : +1 combat skills (left column), +2 armour and shields.
Trog: +2 weapon skills and fighting.
Veh: +1 spellcasting and +3 conj.
Sif muna: +1 magic skills, +2 spellcasting.
Nemelex: huge evo bonus, like +4.

Race favour change of your god (already existing thing, but really rare used) and active usage of divine powers.
Free renounce may be scummy, so probably some penalty should remain.
Also concept may be reffited to some spiritish thing or whatever else.
May be stats should be changed by god too.
Would be cool if every God get some invo-scalable ability only for member of proposed race.

P.S. This post is merely a concept.

I'm not sure if free renouncing really fits the flavor here. At least, to me the flavor seems to be that you're a hardcore zealot of whatever god you pick, and in that case, it almost seems like it would make more sense for you to be locked into the god you pick than able to freely switch away from them. Why would the gods have extra favor for someone who is prone to switching their worship on a whim?

Actually, from a flavor standpoint, this feels more like a class than a race, although obviously the mechanics wouldn't work that way due to how DCSS does classes. But I'm not sure what the flavor behind this race is. Why do the gods all favor this particular race?

Actually, thinking of classes, a "Zealot" class that comes with an amulet of faith, a robe, the god of their choice, and no other equipment else is a fun concept, at least from a flavor standpoint, although it reduces the specialness of the other classes that start with a god.

There's the monk which follows that concept without being insanely OP.

I actually didn't know about Monks getting the automatic ** in piety until I looked it up just now. In that case, yeah, that's essentially a more balanced version of my idea.

Special casing every god to give a species a different bonus was rejected here. I also see most of your other suggestions (Increased piety gain and super high Invocations) in that thread, although nothing came of it.