Given that there's already a system in place to block you from stepping on the area of an empty plot where a house can be built (y'know, that giant orange square), it stands to reason that they could just expand that to the whole plot if you wanted.

I'd also like the ability to pick and choose who comes into my house -- there's nothing in there to hide, but I've heard stories of people walking into their house to see people ERPing in there, which I'd really rather not encounter.