A while back I heard that they made a prototype diesel-electric humvee, with a small engine and 4 independent electric motors -- one for each wheel. Better economy(smaller engine) and manueverability, because it could turn all it's wheel independently (it could turn the front wheels towards each other, and the back wheels away from each other, spin one side forward and the other side reverse and turn in place like a tank.

An idea I had was to have a traditional 2wd powertrain, in a 4wd truck. Instead of linking the front axle to a transfer case, connect it to a generator/motor. Instead of braking to control speed downhill, switch on the generator and charge up a bank of batteries. Then you can use that power through the motor to give the truck an extra push going uphill. Or, put the engine's transmission in neutral when you pull off the highway, and let the engine and turbo wind down and cool off while you just use battery power. Then you get to turn off the engine and hop out when you stop somewhere, while still being nice to your parts.
Likewise, you can start the engine in the morning and just let it idle to warm up, while you start driving right away.
Or, use the electric motor for 4wd. It should be simple to computer control the electric motor and not let it turn faster than the rear wheels.