[thefro526]

It seems like you guys have a good start. One of the things I would suggest that you further research is your need for a second speed in your drivebase. From my experience, and that of other teams, Mecanum drives do not really play enough hard contact defense to need two speeds. Now if you wanted 2 speeds to have 2 different levels of control I could understand. In a few of my mecanum prototypes I made high speed drives that were very hard to control with out a closed loop system but, lower speed ones were easier to control.

But for the gearbox, it sounds like a really good plan but it might not be suited for a mecanum application.