It would only really involve swapping stylesheets which isn't something that would be all that stressful on the server or anything and it's not impossible that this will happen in the future. The functionality is there. The problem is actually doing it. Our basic theme isn't really "done", let alone starting on some more. There's a lot of work involved in doing it properly.
Anyway, it will probably be a while before anything can really happen with it because there's still a lot to do all over the site. Thanks for the suggestion, though!
Edit: Yeah, this thread is ancient. I typed out that whole reply and everything. Anyway, locked now so no more necrobumps.