I'm really late but the comparisons to CDDA are kind of shallow IMO, cataclysm's buidlings are pre-built chunks (just randomly populated with items and mobs) and adding them kind of goes contrary to this game's goals of having everything be generated, which is far off but is the goal.
To be fair, real-life buildings follow certain patterns so this would probably be the best way to do it. Create prefabs for the game to use, sets of furniture/items that match occupant’s civilisation, profession, wealth etc. and voila, a realistic world.
Except that Toady markedly has mentioned many times he isn't lookign to create a "realistic" world, just create a complete random fantasy world generator. He outright mentioned in the big Myth and Magic plans interview he'd like the way the world and culture is built to differ every game and depend on elements of the setting itself - like in a world where teleportation magic is easy, it being integrated into society more than say roads are. Combine this with his plans to eventually make it so that you can have every single race and creature in the game be procedurally generated if you like, and pre-built building chunks would feel shallow and artificial, which to me goes against the point of this project. I believe he's even mentioned plans to completely overhaul the way the entire game world is generated to better suit his goals in this regard, with a total map rework being the first step in the big wait.
What's more likely is that he'll try and make it so buildings generate schematics procedurally, especially as he answered one of my questions a while back about desiring other planes which are just endless buildings/dungeons like some depictions of hell are.
I don't really see the difference. Right now procedurally generated things in the game are made from pre-made chunks and we're all happy. You take a body type, a material, some different biological features are added or removed, and sometimes a special attack, put it together and you get an enormous hairy slug made of filth with wings and two skinny tails, it squirms and fidgets, beware it's fire breath. That doesn't feel shallow or artificial just because I know slugs, filth, hair, wings, tails, fire breath, squirming are per-defined somewhere in the raws.
You can still generate schematics that mix and match different real and fantasy features of a buildings (materials, entrances, furniture, decorations, room layouts, size, tools, populating creatures, etc) from pre-defined chunks, put em together and generate a building. Sounds pretty similar to what people are saying CDDA does.