It is unclear, and I don't recall atm, if the entities in a vet 3 squad recrewing a team weapon retain those bonuses. I think they do.
Vetgate was confusing, and it took months to even figure out (or convince anyone that the evidence was in fact, evidence) so the mechanisms with vet and individual entities is still hard to pin down.
As far as recrewed team weapons having advantages over the initial crew, that is intended. Initial crews are super cheap to reinforce comparatively. Pioneers, for instance, retain their superior sight range, which makes them ideal candidates for recrewing mgs and paks. This is because sight is set by the entity.
Also popcap. I think it was the B4 artillery piece that had all its pop cap loaded onto the crew, rather than the gun, so molotoving the crew and using cons saved you like 12 pop cap.
So it's always been intended. Losing the initial crew is a loss of manpower and vet, but is the most manageable loss. The real value is the weapon itself.
You recall that Obers were rather nerfed? They aren't the same unit they used to be. If schrecks on obers is unfeasible because of their cost, neither are pgren schrecks.
Obers are closer to stormtroopers anymore. And it's not like they or pgrens come close to sufficient for AT.
Ah, so now you provide a bit more crucial information.
So what you're really asking is "how does a USF player handle two players where one spams bunkers and the other covers the position with mortars?"
Get your teammates to help.
You could also use something like a jeep to drive past those bunkers. Soviet clown cars and satchels also help, but since this appears to be a question for USF in a 2v1 situation, I'd say get out of the balance forums and use the state office.
It'd probably easier to just clone the Ostheer sniper, and adjust the Soviet reload and cooldown speed to 133%.
You get the exact same ability to cloak and countersnipe, and end up with a RoF that's adjusted for axis squad sizes.
To give you an idea of how rough just removing the 2nd member would be for Soviets: Currently, at max range, the Soviet Sniper team has a TWELVE SECOND cooldown timer. I'm not sure people are typically aware of this. Ostheer sniper has a 3 second cooldown at all ranges.
A 1 man soviet sniper would need a better vet 1 than the flares. I wonder if the flare revealed cloaked units if it would be balanced.... That'd be interesting to see/test.