I picked up a Gepe 120 tank and reel at a photographica show last year. The reel is plastic, but loads from the centre like a SS reel. It also comes with a film loader/guide that clips onto the reel.
You clip the loader/guide onto the reel and put everything in the darkbag. I then separate the backing paper from the film, letting the film curl under my hand. Then push the film through the loader and clip it onto the centre spike. You then hold the loader and wind the reel. 15s later, one film correctly loaded. Even works when the reel is damp and with creased film (which failed to load on another reel).
Hewes make a similar loader for their SS reels (see here )