I've heard of a certain amount of talk about the possibility of players having individual houses (mostly in the form of people asking for the feature, which has not been implemented yet for various reasons).
One of the reasons I have been told why it has not been implemented is the difficulty of having to find space on the map for an arbitrary number of player-owned houses. This suggestion is intended to demonstrate a way around the issue; a way to have an arbitrary number of player-owned houses on a very small map area.
- The building in question would be presented in-game as an apartment complex. That is, a large building containing a number of apartments.
- There will be a way to obtain keys - either via payment, or completion of a quest, or something. Each key will be a unique identifier, associated with an individual room.
- Using a given key in the right place will open a portal to a room (modelled as a small apartment). The portal will vanish after being used once. (It does not need to be used by the person holding the key - this is to permit ponies to invite others to their apartment).
- The apartment can always be exited, but it cannot be entered without the key.
- People using different keys will find themselves in different apartments (much like the current instance system allows different ponies to be in different versions of Sugarcane Corner currently). When inside an apartment, ponies will not be able to switch instances to reach different apartments.
In this manner, an arbitrary number of 'houses' can be fitted into a comparatively small map space.