This has been done before. Maybe a couple/few years back on BYC.. Sorry I am not able to pinpoint an article but, I recall reading it. The coop was built in such a way that the owner could get his wheel chair up to a side that opened and do maintain it while sitting down. Sorry my brain can't fill in more
Anyway you can build the coop in the garage? Keep you on a smooth surface. Poke a hole in the wall and build the run right outside. Build the "coop" elevated to get your chair under it. Think dinning room table. It can be a simple as as wire cage because you have all the protection you need in the garage.