These are some basic ideas I have about houses, and ways to improve them.
1 ... Manage people who can enter your house

Right now, if you lend out a master house key, someone could make a duplicate of it, and you'd have no idea. They could come in your house, and take everything, and you'd have no idea who did it. What if there was a list, where you could see people who have a key to your house, and you could manage the list (remove/add people). This would also let people actually sell houses. Right now, nobody buys houses because if you put stuff in, the person who sold it to you could have a key duplicate.
2 ... Keys tell where house is

Say you have a key, you want to figure out where the house is. Your best buddy gave you a duplicate to their house and said you could store stuff there. All you know is it is on ____ island. You go to the island, and you search for a while until you find it. This is easier on some islands, but if you've ever tried looking for a house on, say, Crescent Pirates, it's hard to find. What if you could equip keys, and like with Treasure Maps, when you hold S down it shows a map. At the top of the map, it says the name of the island (e.g. Pirates Island). It shows the map of that island, only there are no houses/signs on it. It only shows a blinking X (like treasure maps do) where the house is, so it would be easier to find.
3 ... Keys disappear when house falls down

If you're anything like me, you have a lot of keys. I keep all of mine in a Key Ring of Holding. I have atleast 20 of them, for some reason. What if, when the house fell down, the key just ... vanished? Maybe when the key vanishes, it leaves a note for you (if you're offline, it shows it when you log on) saying that the house has fallen down. This would also prevent people from trying to sell a house that has fallen down.
4 ... Houses sleep when inactive

Lots of houses fall down because people fail to repair them, and most of the time people aren't there to repair them. This could be prevented if houses could go into inactive (sleep) mode when they aren't being used. Perhaps if noone enters the house for a week or two (up to staff to decide) it would sleep. While it sleeps, it dissapears and stops taking up space. It
does lose constitution, but maybe at ~.1% every day, so that people's houses wouldn't last forever, but if they had to go away for a few months it would be fine. Another option would be to put your house in sleep. If you put your house in sleep, it does the same thing, but you cannot get back in it for ~1 week. This way people won't just put their houses in sleep everytime they go to bed.
Please, leave comments on these suggestions. They're only suggestions, so I'd like some input. No need to get crazy flaming them
Chris Zakuto