compact transmission

[Aren_Hill]

i've got an interesting predicament. I've been redesigning and improving our swerve drive from last year, and i've decided to leave dewalts behind and move on to something with nicer ratios. But the problem is the odd constraints on the transmissions size and placement.

A. The output shaft needs to be vertical
B. It would need to accommodate 2 small cims and maybe a big one also
C. It needs to be as short as possible meaning from the back of the motors to the outer plate of the transmission, hopefully around 6 inches in total length, I forget the length of a cim but the shorter the better
D. 3 or more speeds capable of being shifted without pneumatics, servo's or one of the small motors in the kit will be used. preferably servo's
E. customizable ratios.

Any advice?