They just need to make it easy for modders to put their own builds into the same generation pool as existing structures, and maybe their spawn rates. I can imagine all sorts of immersion breaking things happening if they were sourced randomly from other players, but I'm sure that individuals could batch builds into packs to fit different flavours.

It would be great if they could do that with dungeon interiors too. I would be dtf with player made dungeons, even if the interior environments needed to be made painstakingly out of stone blocks. RIP save file size though.