I know this is raining on your parade and I understand sometime the job needs to be done and this may seem like a viable option. I have never done as you suggest, I have use many man lifts. This just my two cents.
After spending over 40 years in industrial maintenance and using man cages attached to fork trucks that were far more stable than a Kubota tractor in an orchard and on a solid flat concrete surface they were still a bad idea, we outlawed and scraped them and moved to scissor, hydraulic lifting or boom man lifts which all have their issues.
I can think of a lot of reasons why this is a bad idea in the best of circumstances, and can see Murphy’s Law coming into play here.
Attached to pallet forks on a removable platform such as a SSQA, the tilt ability of a tractor hydraulic system, uneven ground, possible tip over while possibly moving with a raised load, an adequate solid attachment point for the man basket to the tractor bucket lift assembly so it will not slide off the forks, safety harness and adequate attachment point capable of safely restraining the occupant if he or she were to be ejected. The higher the load the more pronounced any movement felt at ground level will be, as I said possibly enough to eject the occupant. If you have never been in a man cage you will be surprised at how unstable they are and feel and how much they move compared to the ground movement, everyone I know that has used one hangs on tightly whenever they are moving in any direction.
If you are running a business and employees are operating this equipment and you come under OSHA, they may have an issue with your plan, since the man cage has to be approved for use with the individual vehicle you are using it with and labeled so by the vehicle manufacturer, along with many other rules.
In any event if you do, be safe, only move with the load at ground level, and use very slow calculated joy stick movements, etc. Everyone want to go home at the end of the day the way they came to work.
I would opt for the previously mentioned pole saw. Or hire an all-terrain qualified lift and operator.