Soviets are designed NOT to have such upgrades. That is why penals are so strong, because they have to compensate the lack. To overcome this design is not a different play-stile, it is simply a bad design, I would also say bug-using. As stupid as US vehicle-Crews, te decrew should be removed by an auto-repair function too.
UKF can donate weapons to team mates(and crew weapons).
USF can donate vehicles to team mates(and crew weapons).
Soviets can donate fuel to team mates.
Ost can donate resources to team mates.
OKW is all about leeching, so irrelevant here.
Point is, in team games completely different dynamics and rules apply.
You can't remove between faction synergies, because these synergies are what makes for team games.
Each USF donated vehicle is 1 less vehicle for USF.
Each weapon donated by UKF is 1 weapon less for UKF.
Soviets and ost also do not exactly float resources they use for their supply drops and impact of raw resource boost can be greater.
Also, weapons dropping is a thing, you will now want to remove weapon slots form certain units because they might be strong?
Will you nerf HMG42 performance, because once captures by soviets it'll have 6 men crew?
The REAL issue was cons with dual LMGs and that was already addressed ages ago, so instead of bitching about penals with LMGs, how about you'll show us examples from competitive level 2v2 where its used to the overpowering extend instead of whining how theoretically strong it is?