A couple of quibbles, one minor, one major. The minor one is the notion of a Russian soldier putting out 140 rounds of fire (aimed or otherwise) out of an AK in the space of a minute. I'd love to know how Magical Ivan could manage that one. Standard mag for that rifle is 30 rounds, standard drum is 75. Best of luck.
The major one is probably more of article editing than actual knowledge: it's that the author starts off the article arguing for simplicity and robustness and finishes with gear that you have to be an engineer to operate, much less fix in the field. I'm not sure where he got the impression that those computerized sights are in widespread use among hunters. We just don't have that kind of money. Similarly, adding a high-tech suppressor to a battle rifle will cost you range and add complexity and service issues. Are those worth the proposed advantage of making the operator harder to locate?
As for caliber, yes, a new one should certainly be on the table for reasons stated so many times on FR I won't bother to repeat. I haven't any strong opinions on the topic but the 6.5 Grendel sounds intriguing. Got a little range on the 5.56 but not as much as the 7.62. Tools for jobs.
The AR15 platform is very flexible. Every part has to play nicely with every other part, and it’s easy for a combination to go outside satisfactory parameters. Example: an 11”-14” barrel will work well IF you feed it heavy bullets AND have a proper twist; lightweight with low twist and you’re prone to instability (= lousy accuracy). Don’t just slap parts & ammo together and expect it works well. As oft repeated, Vietnam was a great example of what happens when you combine the wrong parts (incorrect powder) and act surprised when it doesn’t work reliably.
Likewise, it’s good for light targets where more rounds per mag = better. Heavier targets will require heavier ammo, which you’ll carry less of ... which is fine, if you reasonably expect fewer targets, more target acquisition time, more cover, and better terminal performance from the ammo.
Fringe stuff like pistons are fine IF you are truly operating at limits of both machine & operator AND circumstances really warrant it. If you’re asking questions like “is the M16/M4 design still crappy?” then you’re not there - stick with Stoner’s design (gas system included) as implemented by modern major manufacturers.