Sam, you're not seeing the forest through all the trees.
Onmilo, I don't mean to be contrary, but I just don't see how the G3/CETME design is close enough to be related in any way to the AK, that the FAL or M14 was not.
You listed a bunch of general design characteristics, or principles, that may be applied to any of those guns to some degree or another (except for the folding/collapsable stock possibility which the FAL and M-14 needed further development to achieve).
The design has nothing in common except.
The reliability, ease of use by unskilled conscript soldiers, ease of maintenance, ease of rebuilding, durable long term reusable
This would unquestionably apply to either the FAL, G3, or M14. Neither takes a whole lot of training for a soldier to make work. All are easy to maintain. They all are certainly reliable. Not sure which is the hardest to rebuild, but all can be.
...truck strong steel magazine assemblies
You do know that most G3 mags are aluminum?
, ease of optic mounting,(at least on the later versions of the AK, always there on the G3),
The AK platform is the hardest of all to put optics on, and the late addition of the side-rail to the AK platform is a compromise at best. There were optics on versions of the M14 before there were any on an AK.
Ability to convert or be converted, to a folding/collapsing stock varient for airborne/mechanized troops. Yes indeed.
Ok. Got that one. That was really an idea adopted from the AK? All right.
What the G3 did provide OVER the AK/AKM was range.
That's a feature of the cartridge. All three choices use the same one, and are effective to about the same range.
This is why G3 and AK/AKM rifles continue to remain popular in many parts of the third world while M14s and FALs, not so much.
As others pointed out, the FAL is still pretty popular, and was adopted by many more countries than the G3.
The primary reason the M14 isn't/wasn't is that we only used it as a primary arm ourselves for a very few years, and really never exported very many of them to other forces, the way the CETME, FAL, M16, and AK series have been.