Fuck, if he plans on doing crazy 4x4ing, he won't need speed, so a full hydrostatic setup would make far more sense. He could have done so many more things with a hydrostatic drive. With decent drive units & lines, there's almost no maintenance involved.
Still, really cool for a RHM4x4...
Plus, he already has a hydraulic system in place. A hydraulic motor on each wheel would do scary things. It'd be slow, but it'd have obscene torque. Just put a bigger pump running off the transmission (actually it probably wouldn't need a trans anymore). It would basically be like the drive system of the Travel-Lifts we use to move boats in and out of the water.