I'm not entirely sure if this is the right place to post it, but what the smeg.
Better villager home finding mechanic would be nice, since now they tend to try crown some point behind a door.
Improvement of that, as I see it, would take adding a "Safety state" to villagers and doors, along with door tile entities, to store it's safety states (two of them), home size, home type (set only by the world generation) and registered villagers, probably other found doors as well, to prevent overcrowding of the house by doubling or tripling the villager cap.
Safety state of villagers is 1 or 0 and is updated on - hit, going through a door with one of the directions having other safe state than the other, or a part of the wall being destroyed nearby, triggering a check from the door they are registered in.
The check is a procedure, that sets the door safety state, basically moves in one of the directions, in a manner of floodfill checking the "room" for consistensy. I'm not exactly sure, what should it do with the slabs and stairs, but oh well. The check is called, when the door is passed by the villager in "dangerous" direction, or when a house wall is modified. I guess there should be a limit for the room size as well.
The tile entity, storing the registered villagers, is used to determine, how many villagers "live" in the house (the "size" part), and to call all the villagers to set their safety state to 0 when the house safety is compromised, or the door is destroyed, also - to call the proper villagers into it in the night.
The safe state of the door can be changed to 1 if the villager passes it, and to 0 if the house safety was compromised, either by destroying the wall or by the villager getting hurt by a mob.
The villager safe state is changed on passing the door in a "dangerous" direction, getting hurt, or loosing a house.
Villagers don't enter dangerous doors in the night, don't call check upon entering safe doors, and pass the doors with safety 1 on both sides without noticing, though something might need to be done about the house size with multiple doors. Hierarchy of doors? Anyway, thank you for reading.
Well, I was thinking more along the way "stop crowding the entrances, you mobs.", as I guess the "natural" house building should be planned by now, with the villager interactions.
The limit of entering is essential as well, though most needed now is some way to let the villagers actually walk around instead of trying to be in one spot.