Profile of Vegatry

-5 or above of baseline infantry like rifleman, grens.
-3 (maybe) or above 'top tier' infantry, but that are some huge mp investment, which shouldn't be much of a problem. (Ex:3 paratrooper which is 1140 mp)
-3 or above of same type of support weapon team except AT gun.
-more than 1 sniper for both OST and Sov, more than 2 for US's pathfinder.

In general, the experience gained by the tank it self "passed on" or inherited to the vehicle crew.
For example, a sherman tank destroy some tanks and achieved vet 3.
Let's say that vet3 sherman was unfortunately destroyed but the crew managed to pop out in time and survived.
Build a new sherman, swap the crew, and voila! the vet 3 sherman is back!

Your points are contradictory, on one hand you want cover to be even more relevant on the other you want smgs to be better, smgs weren't nerfed or anything like that, in fact some were buffed (like PPSH) and thompson are the ones with the highest dps in the game, what changed is the cover and armor mechanics wich became more important after the march patch.

You want cover to be even more important? That will destroy any sort of flank or close range weapon, not to mention will make hmg play even more common.

I don't see your point here, since most green cover are directional except crater created by US or Soviet Engineer's demo charge. Emphasis on cover should therefore promote more flanking maneuver attempt. Thus HMG can't suppress infantry in green cover.

To the topic, we should acknowledge that the fact that there isn't much green cover available after all,yet cover became less emphasized as the game progress. Over-emphasis on cover mechanic might cause more balance issue, such as conscript(s) are either forced to fight grenadier in long range or to charge them but still lose the fight due to punishment for no cover.

For long range fighting, I do agree that LMG shouldn't be a DPS weapon (despite it is expensive) that deals a lot of damage even at long range. Normal Rifle should probably have more accuracy or be more lethal(DPS)than the current state. And I would suggest lowering the hit chance of LMG while increase bullet damage output, one instance is how MG42 for gren used to performed before patched (high damage but low accuracy) compares to its current state.

Conscripts vet3 stats was changed, instead now they gain even more accuracy and additional mobility but no armor boost.