Looks like you have about 30 hp tractor. Now to make the 6-1 conversion work, you will need to run that tractor at pto speed, near wide open. No throttling back as you say, as your tasks are speed dependent.
So, you will be using fuel for 30 hp to run your 5-10 hp items.
Another way to go is run the tractor at idle, and compensate for that with a bigger gear ratio. The problem there is the impulse to run 'just a little faster' and wreck all your implements.
For your applications, a cheap belt setup will work, rather than the $$$ gearsets.
Still not sure it is worth it, use more fuel, more noise, less manuverable, and have to bolt/ unbolt for the different operations.
--->Paul