The MG34 is already a T0 MG in the update, it just requires tech and you're basically sacrificing your T0 production and was already basically possible with the doctrines, well, at least in custom games with High Resources. But I don't see the Brits or Wehr being OP, Brits just have problems dislodging garrisons while USF have smoke and Soviets also have flamethrowers and mortars, Wehr has rifle grenades and mortars while OKW has the Sturmpioneers and Volk flamegrenades, so no, I wouldn't say it would be batshit OP plus you don't have any evidence to prove what you're saying, as I don't either since I already made it in my mod but it uses an entirely different balance than the vanilla game.
I am aware the mg is t0 and requires tech but as i am typing on a phone i didn't bother with an indepth post.
The reason for delaying the okw mg with tech is to avoid situations where you have an mg/sp combo at the start of the game. It is almost with monotonous regularity that okw sends Spio to allies cutoff at the start of the game (1v1).
That in itself is annoying but it would be broken if okw could build 2 mgs, sending them straight to allies cutoff while the kubel cruises around capping everything, then following up with fast luchs which allies cannot counter or at the very least are forced to go at gun because okw has totally dominated the opening.