OK, I just had a crazy idea and I know you guys are going to flame me for it, but.......
What about building a metal box to bury under each tire. Then in said box mount a air powered jack that pushes up on a plate on the top of the box. Lift all 4 up and you would have the same thing as run up blocks. If you wanted to take off a tire, block up the axle and let the jack down on that tire. When it is in the full upright position, place wood blocks between the plate and the ground, just in case you had a jack failure.
OK, flame away.
No flame, but to do this you have to have several things in place. A pretty substantial jack, a mechanism to keep things from falling over with the weight on it, and a way to keep the jack from going down instead of the bus from going up. All it is is money, but cheaper to have the ramps.