Wheel chairs are such old technology. Depending on how disabled a person is, I reckon it would be possible to rig up a segway. Essentially it holds them in at the waist and they do their leaning forward/backward to get movement. As long as they have control over their stomach muscles they should be able to drive it.
I think for it to work, they need to sit in a saddle, so instead of having the bar which you hang onto, it terminates half way (and maybe has one at the back too) and a saddle/harness. Then they just lean forwards or backwards to move.
It seems a much more natural thing than a wheel chair – for starters they are face to face, and they could possibly have their hands free so they can walk and talk and gesture like other people.