I was at one time considering (and still am in the future) making my explorer a hybrid.
I asked Ben Nelson (the electro metro guy) much the same questions, and
he thought having the electric motor situated where you could easily disconnect it from having to turn would be advantageous. What you could do is replace the transfer case with an electric motor, and assuming you have automatic locking hubs, you'd be able to stop the motor from being forced to spin from inside the cab. And by replacing the driveline with one from a 2wd F-250, you'd still have 100% of the normal abilities of the diesel. Having a 5 speed would be advantageous, but you could still reap the benefits of hybrid technology without having to rebuild the entire vehicle. In the instances you actually need 4wd you can engage both the front axles driven by the electric motor and have the diesel engine driving the rear. You'd end up with more horsepower than stock to boot.