To clear up my previous post, what I meant was that unlike you suggested (1*), I was not implying to redesign the lower to Gen 3 pmags, I was saying the MH magwell geometry should be modeled after the gold standard of .308 stanag pattern of rifles, the KAC SR25. This rifle is what Magpul and most other manufacturers are going to use as the bench mark of tolerances. Designing a rifle to one mag is silly just like you suggest, but unfortunately in essence that is almost what has been done thus far with the MH. I am relegated to hunting down mythical G2 pmags and XCR mags. If the MH had the same internal dimensions as an SR25, the Gen 3 pmags would not be an issue, and Gen 2 could still be used as well, along with a duffle bag full of other off brand manufacturers.
I am also curious what all the revisions are for the most recent batch that you hint at in 2*
Lastly I would like to offer the suggestion in reference to 3*, you could find a couple SR25's to measure up, and base your geometry and tolerances off of. This should be an adequate compromise of tolerances and geometry to allow for a reliable use of a wider variety of .308 stanag mags. If it works for the KAC SR25, it should be transferable to the MH since they share so many basic characteristics together.
Lastly, in my opinion, I would rather improve upon the design, rather than have a work around. Always room for improvement, and this would be a good step.