I wouldn't be too concerned about having to remove the swingarm to change belts, my new CB750F1 came with an "endless" chain, and the owners manual advised that to remove the chain, you had to first remove the swingarm, and this is also the case with most modern bikes, as fewer chain suppliers are providing joining links with removeable clips nowadays.
I recently aquired a new RK X Ring chain for my racer project, and I have to find a chain rivetting tool to properly join the sucker, which is a pain. Terry Q is quite correct re: the tensioner, the belt remains in constant tension, regardless of the angle of the swingarm. Problem with our bikes is the distance from the swingarm pivot to the front sprocket, on modern bikes, the swingarm, in a lot of cases, is hinged off, or very close to the rear of the engine, thus placing the pivot point a lot closer to the front sprocket.
I guess the ideal set up would be a CB750 engine in an old Santee or Amen Hardtail frame, that way there would be no need to constantly tension the belt, as there is no pivot point between the engine and the rear wheel. C'mon you chopper guys, lets see the first belt drive SOHC-4! Cheers, Terry.