The Gen II mags are not modified M14 mags, they are designed off of it. No different than Magpul designing their mag off the SR25/Original Armalite mag. The only downside to the Armalite Gen II mag is weight. But weight could be cut down using stamped aluminum, it would take a bit of research sure, but could be made just as strong as steel, with the exception of crush resistance. But with technology available these days, it can be done.
People are just scared of investing in something new, too afraid of failure. As is the public anyways skeptical of change or straying from the norm. But that's where breakthroughs happen, where new things are learned, from venturing into the unknown.
It's a damn reliable magazine design, but Armalite does not play nice and refuses to let other people design lowers to use their mags. That's my assumption anyways. Only ones were Aero Precision because they made their receivers for awhile. Iron Ridge tried, but got sued by armalite for using the "-10" nomenclature and I believe for using their specs for the mag. They wouldn't go after just the use of numbers, atleast I think that would be a waste of time.
I'm not saying one design is better, or there should only be one. This isn't The Highlander. There can be multiple designs, variety is the spice of life. Armalite designed a damn good system, and I don't understand the amount of resistance it receives. Screw armalite as a company or their cockiness regarding their name, it's a great design, that works very well, and I think there should be more third party lowers that use their mags. That's all I want. Options.