I'm not trashing your attempt at a labor saving device, but I would be rather afraid to trust it very far. Too many chances that something "unplanned" might happen. I realize the hydraulic lock-out, the rear backhoe as a counterweight, and the stabilzers are all pluses...but.
I know, their are scissor lifts that will do this very job but the difference is that they are designed from the outset for this very type of use, whereas your tractor is not. I've seen people use their loader as an impromptu scaffolding before and I've never know any of them to get seriously hurt, but I still wouldn't try it myself.