Just bumpin' this so you can maybe get an answer. I'd like to know, too, since a power reverser would save some money. Without getting into the whole Hydrostatic vs gear issue, I think the power reverser could be the best of all worlds - especially for ground engagement work.
I think what you are calling a power reverser is what I call a shuttle shift if so my l2250 had one and as a gear drive tractor if you set the hand throtle it was the same as having cruise control Randy
John Deere 4052R Cab,, Deere 855D UTV, Z920A Zero Turn Mower and assorted implements
Like any gear transmission, one sets the throttle (hand throttle) at a given RPM and the tractor moves along. There is no need to use the foot throttle unless you want to increase speed momentarilly.
So, it's not exactly a "cruise control", but the operator does not have to push on a pedal continuously.
I do have a reverser transmission on my Deere 4400, BTW.