What I would really like is to be able to take over one of those fabulous redoubts that I've cleared in the Reach, clean it up and build a palace there. Talk about a view!
I'll ditto that! ^
I think just starting off with truly "open" floor plans for the houses you buy would be fantastic. It might be rough, and would likely require some small "construction" program that you can somehow access in game...but it could be done I'm sure. I'd like to at least move the furniture they give you around, or maybe ditch one furniture item for another, like more containers, or another set of shelves, maybe a few more wall hangers for weapons. All depending on the house of course.
I know that there are legal-logistical things that would likely not make the venture not worth it of Bethesda, but I have always wanted to pop in a "construction kit" disc into my Xbox360 and create things, save them onto a thumb drive then load them up into my game when I turn it on. Or! just make it so that I can build it on my PC, then drop it onto a thumb drive and load it that way. That would be....epic.