Finding a mower with Schmidt mountings is hard work, unless you go for something like a ducker or Mulag fme mower, then you're looking at lots of pennies

you could mod a mower to fit Schmidt mountings, the only difficult thing would be pto angles as the pto joints with a Schmidt mounting are very close together, hydraulic would be the answer.
As for mounting, wind up or hydraulic legs

very easy once you do it once or twice

6x6 thing is cool, not sure if its an original factory job looking at it tbh. If not its an unbelievably tidy job. Shame if they drilled and extended the chassis though :/