I have an idea for owners of 4X4 trucks, I own three so it hits home.
Since it's spring and I don't need 4X4 my thought was this:
1) Disconnect the shaft from the transfer case to the front axle.
2) Connect a forklift motor to the transfer case.
3) Get some cheap batteries or an ultra-capacitor.
4) Wire up a button on the steering wheel to engage full power, no control, just power. KISS
5) Wire up a relay to the brake pedal to provide charging for the storage.
That's it, again KISS.
Oh, for those of you that don't know, KERS is
Kinetic Energy Recovery Systems