I would be interested in something like the Magpul L-Plate, adding a rubber bumper to the bottom instead of the loop.

I don't think the 10-round short magazines need a loop since they're less likely to be needed from a pouch in a hurry, and also would benefit less from having a good amount of length added to them.

Although I do very much like your design. Where were you when I chopped the bottom off of one of my magazines and glued a ranger plate on there?