I am marlon506 and I am high bidder.
If I don't win, I hope that SOMEONE here does get it.

So instead of 2hi, 4hi, auto and manual modes, we can do an AUTO, MANUAL, 4HI.
That sounds reasonable, and the manual mode can be controlled via potentiometer (by modifying the control voltage to the timer circuit).
We can use Bob's transistor arrangement to control the dash lights.

The only catch is:
We can only vary the torque to the front axle as long as it is GREATER than what is actually required.
If the speed diferential between front and rear axles is too great, then expect the mechanical 'clutch' to engage the front axle. So no donuts or dynos in 15% mode.
I can live with that.