You could always use a holster to change mags. Just put the gun in the holster 3/4 of the way and hit the mag release. Then put it all the way in the holster, pull the mag out and put a new one in. There's no rule against this as long as the safety is engaged. You could charge the gun this way as well as long as the safety is engaged first. You'd have to rack the gun when you uncase and engage the safety, holster, mag, rack, safety off, low ready... Could also get the slide racker style thing (bar style, not the ring) that goes on the back of the bolt and just hook that into your belt to run the bolt
For loading mags that cheap red thing that holds the spring down would work you'd just need a way to hold the mag upright. Possibly if somone could make steel basplates you could put a magnet on top of an ammo can to hold the mag or something along those lines.
There's dozens of ways to adapt. If you need anything made or welded feel free to send me your number I don't charge any money, just shipping