"but personally i think that every faction should have a few core units, that they share with each ohter..." Just as a heads up, after that is where you state why. Otherwise you're just rehashing conversations that have been had umpteen times already up to this point.
Ostheer and Soviet... are just two different versions of the same army. Cons are Grens, Maxims are MG42s Stugs are SU76s, T34s are P4s and so on.
I don't mean to be disrespectful, but I think you need to take a more in depth look at unit statistics or see a few more in game scenarios if you consider these factions/units to be at all analogous to one another. This statement is also very counter to the point I presume you're trying to make. Unless that is,
the WFA's should be more like the vanilla factions. in which case you should just come out and say it.
And in case this discussion does get expanded upon. I agree with Lemon. Strategically each faction has the capability to do the exact same things, only this will manifest itself through different, unique tactics. Each faction also adopt different postures and execute different strategies more effectively than others, not to say that they can or can't do specific things.