Objects for player housing data.... interesting. Trying to invision how this would work, but it's an interesting idea and would solve at least the problem of having houses left over after players deleted. But since a house ( and by extension a guildhall ) is a physical structure in the mud, it doesn't make sense for it to be something tied to a player. Player deletes, objects goes, and somehow house just up and disappeared?
The UO idea sounds cool. If only an automated way could be found to do that to normal rooms and have them simply evolve after a player's destuction to have the whole thing decay over time. It works in UO because it's graphical and all they have to do is run a "decay" algorithm on it against a few known tile sets. Text is far more dynamic than that and you could have any number of descriptions and map layouts for it. An active imm staff could monitor time passage and edit descriptions to show the state of decay, but this involves much manual labor.
If another player comes along later and sees this abandoned house, they should have the option of filing a claim for it to take ownership as well. Which brings the property code thing into play. Deeds and the like. If a player deletes and owned property, it should be treated as though they died and the government should assume ownership somehow. Even if this would be unrealistic for some old hermit hut in the woods, can't just let players take stuff like that. It would throw the balance of things off.
As for OLC - never. I can't see any good way to allow them even limited control. The potential for crashing the game is just too high no matter how well the system appears to be running. Players are notorious for finding obscure flaws and failing to report on them