actually you did. But it's ok.
Since I haven't worked with an arduino too much I still think I would go with the mega since I barely know programing (not my filed of studies), and at the same time i don't know anything about I2C protocols or 1 wire-protocol.
My house is not big, it's a 3 room apartment around 60m2 and the controller will be in the center, so I have no problem wit the length of the cables.
Right now I'm trying to decide what to buy in order to start working with arduino and familiarize myself with it, but at the same time, I'm a student, so I can't afford buying more than I need. In this case I want to buy one micro-controller and use it for learning and then to put it in the project.
I'll look also into your Idea.
I thought about buying the starter kit because I get the arduino and display at a pretty decent price (all the other passive electronics are useless to me, since I already have a breadboard and a full storage room with passive component at the university lab)