Yeah, should be fairly easy to implement just by (optionally) let the player specify a (safe) room height during guardian setup?
Question is if that would be enough since usually its just individual objects such as fans and lamps that pose the danger. I wouldn't be happy with having to set the whole guardian layer of the play space to minimum height of these...
I need the roof option too. I live in a top floor house and ceiling is shaped triangular, in one side of the room height is enough but on the other side because of the roof shape the height is getting smaller. Because of that while playing Half Life Alyx and throwing a grenade I hit the ceiling and controllers got scratches.
I've hit my ceiling fan more times than I care to count, and one of these days I'm worried I'm going to break my fan, my controllers, and my hand. I checked out the Ideas board and it looks like people have been wanting a feature like this for years. I haven't heard of any plans for it being implemented, but hopefully they will add it eventually.