This might have been discussed before, but there's ideas getting thrown around here: beta.glitch.com/forum/gener...
The ability to expand your own house is a hotly discussed topic. I remember we discussed carpentry abilities and the idea of expanding your cabinet space. I think it would be a fun solo-type project to be able to climb the Bureaucratic Arts and maybe a Carpentry skill tree to expand your home to include a basement (for those houses in the Meadows and Forest areas that want dark patches and Jellisacs) or a Greenhouse (for Shimla houses that want gardens and patches).
You'd have to get your permits from the Bureaucratic Hall, and then maybe ala the Street Projects, start a House Project where you have to go and harvest planks and maybe dig the earth from your house and get rid of it somewhere (donate it to Projects! Full circle!) and then you might need to pay for a "Contractor" to come and finish the job for you.
Just throwing out some ideas, because I really want a basement in my house!