If you've never seen the PTO you don't see that the spool can spin loose on the shaft. The knob had nothing to do with the capstain drum. It operates a collar that locks the cable drum to the shaft. That is the way you keep all the time except when free wheeling cable out. Otherwise the drum would turn and the cable would start to unwind. The little piece you see on the brace next to the capstain drum does nothing. It's just the same brace as next to the cable drum. The hole is where the arm that engages the collar on the drum pivits off of. That's part of the reason I think this was never offered as a option. If it was a Toyota option they wouldn't have bothered to weld that piece on the end brace. That and the fact that is doesn't have the Toyota hook and chain on the end of the cable.
This wouldn't really be hard to do. All you would need is a longer shaft and capstain drum mounted on the end. Then just use another end brace like the one next to the cable drum.