So, how are you dealing with the wiper park switch stopping the wipers in front of your field of vision? That is why I went with the CJ stuff more than anything. I had a YJ motor laying around too, but the park switch on those won't stop the wipers until it gets in that park position which is right in front of your face. A CJ motor allows you to stop the wipers anywhere you want.
That extra wire is for the park switch. It provides power to the motor after the wiper switch is shut off to allow the motor to continue to move until it finds the park switch. Maybe if you cut that wire out, it would work like a CJ motor.
Also, the CJ wipers are two speed, so there is no difference between the CJ and YJ as far as more options.
The CJ wiper control switch is also much better to use for the flat dash of the M715, since it is used in the flat CJ dash. The YJ switch is the type that is on the little stick on the side of the steering wheel. I suppose you can use a three position toggle switch that would allow you to keep the two speeds.
I guess I may have answered my own question. I hope it works out for you.