A synthetic "village" biome, to add buildings to villages. Try to avoid creating villager deathtraps (doored but incomplete buildings).

A command to locate the nearest ruin, and say whether you are currently in a ruin. If there is one, please document it, I just looked and didn't see anything.

ETA: Go ahead and special-case the End as well as the "Village" biome (and the Nether), to only get biome-specific ruins, not biome-generic ones.

End is a biome, isnt it?

Well yes, it's the Sky biome. Which is why it ought to be trivial to not put generic ruins in the End. Something End-specific, sure -- odd structures of End materials, or even buildings from prior explorers (not necessarily dragon-safe, even), but not the same stables, farms, and orespikes you've been seeing all over the Overworld.

That is not how villages (and other mc structures) work. Basically the game tries to find a spot, similar to how Ruins works, then "unfolds" the structure from a central spot using premade puzzle pieces. Yes i kinda copied it for the "adjacent" Ruins tech. But what i'm saying is that Ruins does not offer "attachments" to this or a "biome". You could create your own Ruins-powered village using adjacent rules.

The commands are possible, but no, they dont exist yet. I'm putting them on my wishlist.

End is a biome, isnt it?

It is trivial, just go through the generic ruins and add the end_stone or whatever it is called to the disallowed blocks

OK then, I'll modify that suggestion to exclude end_stone. It's just silly to go to the end and see all the familiar ruins somehow littering that exotic dimension..

I agree the default Ruin set needs work. Constant maintenance, even. And i freely admit i can't or won't do that as much as needed. Don't have the time.