You could build a pto powered driver. Here on smaller work barges they take an aold rwd car drive train and put it on a frame. Just the engine trans and rearend. They make a frame to hold the rear axle and then cut a section of tube out of it. THe frame holds the outside bearing and axle. THen they pull the live axle out and make a spool to fit it. Then hold the spool in the place where the axle was and slide the axle inplace through the spool. Then welde the spool to the axle. This is how the old pulp loaders worked. You just apply brake to the one drum and it causes the spool to winch up. Then you can use the brake to hold the drop hammer. We use these from time to time on the water. Sometimes run off electric, or a hydraulic motor.
You could make the frame and winch one set up and run it off the PTO. It can be made from a golfcart rearend to. The other one is whats more common now. They make a driver from an H beam and then ue a 6 foot 2 inch cylinder to with a simple sring loaded pin in top of it. It will pop into a torched square hole intop of the drop weight. My friends rig is a large one mounted on the end of an old prentice log loader on his barge. It will drive some huge posts in the ground.