Heck, if they'd just make it legal to slip the magazine behind your belt and trap it against your belly, instead of requiring some sort of magazine holder, that would be 90% of the way there for the "start-with-all-your-mags-on-the-barrel" stages.
Technically I guess you could do a ghetto version of a magnetic magazine carrier that really relied on trapping the magazine between your belt and belly. Sew a pocket for a flexible refrigerator magnet on the backside of your belt, so when you tuck your magazine behind your belt it's theoretically attracted to the magnet, but is really held by friction. There is no requirement on how strong the magnet has to be, just that it has to exist. Just like there's no requirement that an attached light output a certain amount of lumens, just that it does emit some light.