spinning ball nuts

OK, new idea for my fast running long axis CNC router. The overall
travel the long way will be about 100". From all of the mechanical
calculations to attain the rapid traverse speed I wanted, out popped
an unrealistically large diameter lead screw solution (financially
unrealistic, that is). So, instead of putting in a 1.5" diameter
screw and spinning the screw, I'm considering a smaller dia.
stationary screw and then spinning the nut (can go as fast as I want
then). Besides the added design challenge of having the servo motor
move with the gantry that it drives, what snafus might I encounter
with this approach? Anyone have any experience using spinning ball
screw nuts instead of spinning the screw?
Scott