Direct drive the middle wheel from a live axel, and run chain out to the other two, that way... no single chain failure can cost you an entire drive side. The only downfall is that you have to make custom hubs for the middle wheels.
In the below diagram... the blue is the chain, the black rectangles are the wheels, and the yellow boxes are the Dewalt Trannys. The middle wheel would be driven by the grey box, which is the live axel... The outlying wheels would be driven by chain and ride on dead axels.
Edit: I know that this would only use two of the motors... but it would be very easy to go with a setup like the one below as well:
You would just need to machine more hubs...