How to choose a valve to use when plumbing a huge valve handle to my hose station
It's true that is a lot of leverage for most valves that would be appropriate for a water hose.  A large gate valve might work, but you would get a full stream of water even when the valve was opened 1/4 of the way (depending on size, of course).

What I would propose would be a few gears (worm/screw drive?) between this large handle and a 3/4" valve.  If using gears, you can make a large, strong axle to hold the large wheel rather than having it mounted directly to the valve.  The torque available with the large handle could still be a problem, but mechanical stops could prevent over-torquing.

Another idea - use an electric valve to open and close the water hose, sense when the wheel is turned, and activate that valve.  This way you can turn the wheel as much as you want and as fast as you want and the real work is mechanically separated by the electronic valve.  Also, you could design in a timer to automatically close the valve after being on for a set time.

I realize building something like this might be beyond a small DIY project, but it's the best I could come up with beyond using a large valve.  And who knows - you might really enjoy the mechanical or electronics challenge.