Has anyone tried putting a variable resistor in the down circuit?

1992 XJS Convertible

The problem is that sometimes the motor winds the window down so tight that it cannot get turning again to raise the window. I took the motor apart but found very little wrong, only a black streak on the commutator, possibly from a speck of grease.

The window was wound down very tight against the stop. Compare it to a bolt, you can spin it easily in the thread but after you crank it tight with a wrench, it can later require more torque to loosen it than when tightened. I am thinking about putting a variable-resistor between the thermal-breaker and the down-relay. Then the power can be throttled back going down but will be full power going up.

Am I crazy or will this work?
If so what resistor should I buy?

 

I reassembled the motor and bench tested it. I could not make it get stuck. So maybe that black streak on the commutator was the problem.
It is reinstalled in the car and is working. If it ever gets stuck down again I will try my idea.