I used to bike with my Maltese in a pack on my back. He loved it. He was a good apartment dog too - the only downsides were 1) health problems and 2) monthly (at least) groomer visits.

I would not, however, train a dog to use pads. Our experience was that it took longer to house train, and our dogs got really confused - they thought it was OK to go anywhere in the house if they could go in one spot. I know our experience is unusual - I just wanted to throw it out there.