I've never suffered (though I probably will in a few years T.T) so I don't really understand your range of motion well. But my wrist only twists very slightly to reach c/v/b. 5-6 kill me though. Do you have your hand at an angle?
You could consider going to edsf as your movement keys. I've heard that can help.
One thing I tried (didn't work for me); was binding mouse 4 and 5 to shift and ctrl (using a program I can't remember). And used them as my modifiers.
What I really wish is they'd let me bind my goddamn scroll wheel to something other than the camera zoom. I've always preferred that for selecting targets.