I'm posting this to a couple of forums. Not sure if you had it in mind when you designed this, but this is screaming to be installed in underwater ROVs. Proportional speed control of the thrusters is a bugaboo that's been tough to chase down for the competitions out here in Hawaii, and it looks like this would be a drop-in solution.
I had in mind using two of these in an IP66 enclosure with hermetic connectors (Bulgin Buccaneer makes inexpensive connectors along these lines). One controller would drive the fwd/rev/turn thrusters and the second would drive the up/down/tilt thrusters. Aux outputs could be used to drive lights, ballast pumps (in case the ROV is expected to lift loads), or a manipulator. RC can be fed to the underwater ROV using a coax cable as a waveguide. The core is left bare inside the IP66 enclosure as an antenna, and the RC receiver is placed in close proximity to it without making contact with the antenna. For about $250 to $300 using a radio off of Ebay, this would give really nice proportional control over an underwater ROV. And with the mixing options available on the TReX it would be remarkably friendly to drive.
Longer-term this also gives an upgrade path to embedded control of the ROV for semi or full-autonomous operation.
If any teams wind up going this route I'll ask them to get on the forums and post their project details to the forum (but probably AFTER the competition...)
Man, this rocks!