Honestly the only one that makes sense to me is the one below the Dorm Room. Because sometimes you might fall out of the map endlessly.

I would personally say have the option to turn it on and off, because i think some people could find use out of them being turned off, but some people might want to keep it on, i dont see any times where people would, but they could

Or make it scalable like an AI zone with maker pen

tbh they should remove to kill barrier and add a kill barrier thats only on the floor below the map incase you fall down. Plus it would be a ways down so you can build basements and stuff.