Isn't the rate of "linear" motion related to the rate of rotation in this design? So wouldn't slowing down that rotation, in turn, slow down how quickly you "move" around the field?
I also question the safety of this design on the FRC scale. Even if you keep the design relatively compact (say 18"x18" without bumpers) and rotate at the bottom end of your suggested range (120rpm), the outside corners of your bumpers are already moving faster than 1000 ft/second. Much worse are the hard corners of your frame (which are traveling 800 ft/second). There's a reason that videos like
this one give warnings about "melty-bots" being able to
kill you if they're out of control. There's a reason why these types of robots are mostly seen in robot fighting, because their very functionality relies on large amount of kinetic energy.