I'm on the list for the VERSA-12 for the M11A1 and Glock mags. I have a MAX-31k upper for the gun, and that covers the Suomi drums and coffins. It runs like a top and I love it, but I don't like the Shockwave Z-S mags. They are hard to load and not super reliable in my experience. Plus, being out of production, they are also expensive. I don't think that Glock mags are the best SMG mag, but they offer a lot of advantages, including cost, easily available mag carriers, easy insertion into the mag well, and the ability to swing a dead cat and hit a Glock stick mag just lying around anywhere in the country. Since I have a number of 9mm Glocks and several 9mm ARs that use Glock mags, it seems like the obvious choice.
That said, I have a BRP-Stemple gun that uses Suomi sticks, coffins, and drums. If there is an adapter for just the stick mags for the VERSA-12, I would consider adding that on at some point. I also have a bunch of Scorpion mags, so I might get an adapter for those. While there is not presently an Uzi adapter on the list, if there is at some point I might be interested in that. I have a M10 with an Uzi magwell and therefore a bunch of Uzi mags. I also have Colt 9mm pattern mags. Basically, I can use just about any of the present or future adapters. Ironically, the one I don't have mags for, and therefore wouldn't be interested in, is the MP5.