Unless Mr. Lage wants a bunch to sell with his uppers it doesn't look like S mags make sense. 1000 mags is a lot to sell when there are already a bunch out there so people like me that have some (6) won't want to buy any more. MGs are a niche hobby, the Max-31 is a sub-niche and the S mags are a sub-sub-niche.
It looks like the best alternatives is that some one has a bunch of adapter tabs made on a CNC as well as a jig to weld them on and a tool to modify the feed lips. More hand work and so a higher piece price but you can do a run of 50 and make it worth your while. The competition for a Max-31 stick mag is the 50 round coffin mags that are $100 and up so you might get $50-75 each for a Z mag reworked into an S mag.
The other alternative would be for Lage, PS, or Shockwave to make a run of the Strobro Franken-Magwells that allow the use of the Z mag.