Ideal 4x4 System

If you have two wheels "high and dry" then they aren't touching the ground at all and sending the torque to them won't do anything for you. Those wheels would just spin in the air.

The idea of a limited slip system is that the differential can detect if a wheel starts spinning and it assumes that the wheel has insuffucent traction so it applies more torque to the opposite side of the axel which is presumed to have better traction.

What you are, i think, attempting to describe is a manual version of this.

I doubt a person could make better decisions then the mechanical systems of the vehicle itself without getting stuck first (The vehicle does this all the time and shifts the torque so that you don't get stuck to begin with).

The other option, of course, is to go with a true locker which would apply full torque to both wheels on the axel at the same time so that it wouldn't matter if one had more/less traction that the other. With a locker in both the front and rear pumpkins of a 4WD vehicle you can have full torque applied to all 4 wheels.

With the use of a "Air Locker" type of system you can switch from a limited slip to full-locker system with manual intervention.

By high and dry I mean two wheels are down in a muddy rut and two are up on solid dry ground. Course you were "funnin´" me. I had a vehicle with limited slip rear end but the problem was it had to spin a bit to lock up (start limiting slip) by which time one side was pretty well burried. I have been in off road situations where I would really have liked to pick the wheel or wheels to get torque such as on a side hill close to a drop off. In such a situation by the way two lockers could have you spinning at both ends moving you down hill towards the drop off. Systems allowing you to manually lock front or rear axels or both (some German vehicles I think) are of course a step in the right direction. I grant that the transfer cases on all wheel drives that direct torque automaticlly to slipping wheels no doubt work well most of the time.