Ok *NOW* my ambitions are set high enough (and my level of insanity is thus proven).
So I've started the planning of this project. I've been able to snag a few fan-based basic designs for K-9 off the internet. Rough base dimensions put the little guy in at about 18in wide, 18in tall at the shoulders and just shy of 30in long (not including tail or head). So K-9 isn't terribly big (smaller than I expected honestly). So with that found out (and I'll probably be insane and double check them based on extensive video watching), on to locomotion.
I could do this with an insanely simple 4 wheel drive setup, it would work, be relatively simple, and still mostly achieve my goal. That said it won't climb stairs, so out the window that goes. A quick survey of stair climbers reveals a few base types, most of which utterly suck when going over a flat surface. I also have the added constraint that K-9's base doesn't (in canon) angles upwards ala a pyramid, which makes concealing things a bit harder (and it means there's a couple of drive types that just won't work. My current thinking is to go with a set of tank like treads that can climb stairs (a la the irobot packbot), and possibly provide a hydrolic backstep (horizontal to the base) to level out on something like the escalator:
I think step 1 for now is going to be to get a base with some tank treds on it and start experimenting. This does mean I need to investigate motors, motor controllers, and tank treads and dedicate something to the initial running of those pieces.