I thinkk you can get an R1100RS for under $5k. The maintenance is very similar to an airhead, excepting you need two sets of feeler guages. The throttle setup is different, too, but there are lots of tutorials on the net on how to get them set, and otherwise they use your old friend, the Twinmax, to balance them. Oh, and you need a alternator belt every 36,000 miles.
Just as with the airheads, what weak points there are, are well known, as are the fixes.
And you get double the HP, modern brakes, great suspension, 800 watts and radial tires.
I have 209,000 miles on my R1100RS. It hasn't been completely trouble free, but what difficulties I've had have come after it had 150,000 miles on it. I had a 2002 R1150RS that I put 86,000 completely trouble free miles on.
Regarding the CANBUS, what is there to buy that says CANBUS on it? I bought a Fuzeblock for my R1200ST, so that I could add accessories without worrying about the CANBUS. The extra socket I put up on the dash was then trivial to add. I also put a flashing brake light and a real horn on it; that wasn't any different than doing the same thing to an Airhead.