the real problem is the pinon gear wont stay stationary relative to the steering column not only do yo have to deal with it moving vertically at the same time it can be twisting.
very nasty bump steer
PTO shafts only move in one plane.
straight front axle move a point moves in more then one plane
I don't know how much twisting of the steering shaft would take place as a result of suspension movement...I do believe there would be a noticeable amount of vibration transmitted up the steering shaft to the driver.
PTO drives on Ag equipment do move on all planes. Along with the side to side from turns, there is also a constant up and down and twisting as the tractor and implement travel over uneven ground.
