[GeeTwo]

There are plenty of whitepapers and such on CD about robot drive system design. As you look at them, be aware that your vehicle will need to support a heavier payload (200 pounds vs a game piece or two), and that FRC robots are designed for a flat floor and carpet as the primary surface, with an occasional well-defined platform, ramp, or bump. The 6-wheel skid steer most typically used in FRC has the center wheels dropped about 1/8", which is enough to shorten the wheelbase for turning - on a flat surface. Off-road, this will not be the case, and you would often find that you are unable to turn.

I also did not notice anything indicating that you were in competition with another similar device, so speed is probably not as important as getting there reliably.

I would therefore think more in terms of a pickup truck than an FRC robot in looking for candidate drive trains. I would consider rear-wheel drive, with front-wheel linkage steering. Steering might be powered through a lead screw, and the rear wheel drive system might feature a limited slip differential (better performance) or separate drive trains (simpler).

Edits:
Definitely use a larger battery than we do in FRC (18 A hr). A big deep-cycle marine battery is probably the ticket.

You'll need a suspension. Leaf springs look simpler and more reliable than coil springs and shocks, but I haven't designed with either.

Don't forget to seal the gearboxes and motors against mud!