Hundreds of scripts changing RotVelocity every step? That sounds very bad and unnecessary. Try have one script that loops through the parts you need and change them from that instead of having lots of separate threads.
Also, what do you mean by Velocity doesn't decelerate? As far as I understand, both rotVel and Vel decelerate.
Regardless of that, I think having a bool property or maybe even a vector3 to define how much or whether or not either property should decelerate would be very helpful and eliminate the need for clunky Body(Angular)Velocitys when you don't need the MaxForce property functionality.