"one 7.62 rifle per squad for anything the m4 cannot handle"
What do you suppose an M4 cannot handle? Im sorry but we arent fighting adult elephants, but humans, also Im sure with a well placed shot even an adult elephant cannot stand alive to a 5.56mm.
"a 5.56 will NOT penetrate thru an 12" ebony, mangrove, or teak tree at 300 meters, the 7.62 will."
No, but again, a human is not a 12" tree, a human with the best helmet to protect his head at 800 meters will have a hole straight through his helmet, and his head. Im sorry but apples to apples. Your comparison with the 7.62x39 was good, and its effective range is better than the 5.56 under 100 meters, beyond 100 meters and going way beyond the 5.56 will outperform it.
In Iraq the enemy did not have that many wounded by our 5.56, most of them did not survive, and we could shoot well beyond their AKs range, and kill them fast. Keep in mind many advances and differences between the vietnam era m16 and the m16a2/a3/a4 and m4 have been made.
"1. Cheaper
2. Lowered the physical prerequisite of the infantry personnel"
One I agree with, 2 I do not agree with, it did not lower the prerequisites of the infantry, in fact today the prerequisite for infantry (at least when I was in) were alot higher than back then.
But it did allow the infantry to carry FAR MORE rds, and be able to assist the unit, in carrying other needed ammo, and supplies, grenades, etc.
"And NO way will current 5.56mm ammo penetrate a Kevlar hemet at 800m get real"
Sorry but Ive seen that happen first hand, the 5.56 will go straight through a kevlar helmet at 800 meters. It will also go straight through a steel helmet at beyond 800 meters.
Using a 5.56 against an automobile to stop the vehicle in motion takes a bit more skill than using a more powerful rd, but using them against a human there isnt much that will allow that human to get back up.