SoundGuy, Try as I might I just can't undedrstand why you make a statement about holding your foot in a single position for hours. I have never done or thought I would need to do that. Even if you did, the ergonomic design of the Kubota HST pedal would make it pretty easy but it sure isn't required.
Cruise automatically turns off if you tap the brake or move the HST pedal. Cruise really does work neat. If for some reason you didn't want to "disturb" the cruise setting and only needed to slow down but not completely stop, you could ****** the throttle and the clutch is available if you want to completely stop without changing the cruise setting. Normally I only use the clutch for starting (lock out switch) and for engaging and disengaging the PTO.
The only time I ever held my foot on the pedal for very long in one position was all the way forward which is not particularly tiring as you can hold it with a toe, heel, left or right edge or whatever, not a cramping sort of thing. No more tiring than just having your foot resting on the floor.
Of course, with experience a good operator such as yourself and many others here learn to optimize their performance within their tractor's capability. Irrespective of what equipment you have, as you indicate the operator is an important part of the mix. Not everyone is cut out to operate equipment and there are no current designs on the market that can make everyone a good operator. I suggest the HST comes closest.
Pat