Its a grand Idea Ed, one I am almsot certain a\has gone through developers minds. The problem with it is, housing itself is "HUGE" its your own part of the world, a section of the UO server desinated to you alone. That actually takes up alot of server space and tweeking with the housing system in any way other than adding tile sets is going to be a long time in comming.
I know I'm being doom and gloom, but it is a great idea. Might see it by the 24th anniversary.
P.S. your second solution works similar to being a friend of the building. But I think I get where you are going with it. . . maybe. . . then again I confuse easily.