Uh what? Infantry with Machine Guns don't fit Germans and IS-2 Heavy Tanks don't fit Soviets? What war are you thinking of?
I think of Soviets at quantity of T34 tanks, and Germans as revolving around heavy machine guns. In German infantry doctrine the main element of firepower was the MG42, compare this to the Soviets or Americans which favored greater individual firepower at the expense of squad based.
In game terms, this should translate to rifle squads/ cons having a greater role in infantry combat than HMGs, with the relationship between Grens and the HMG42 being the opposite.
In game however LMG Grens boost their squad level firepower to the point where HMGs aren't needed and Gren squads gain fire superiority themselves. If Gren only infantry fighting strategies were meant to be employed ingame, than Grens would be the T0 unit, just like Riflemen.
I personally think that the LMG upgrade should cost 80 muni, or be nerfed.