Consider what OKW units can suppress:
-Kubel
-Flaktrack
-Luchs (if vet5)
-T3's gun
-ISG
That makes OKW not only the most non-doc units capable of suppressing but they re all spread in different tiers. And that's not counting doctrinal units: MG34, flak emplacement, bunker,
Of all the factions, OKW has the most suppression options, and without having to choose doctrines. There is no lack of suppression as OP claims, and that is ignoring the fact that he doesn't care if the repercussions bring about more imbalance.
Options:
1. The kubel rarely lasts past 5 minutes; mid to lategame, it gets basically 1 shotted. Even if it does, it's generally not worth the huge amount of micro it takes to keep it useful.
2. Good luck getting a vet 5 luchs or obers. That's not a reliable source of suppression, and it isn't AOE, and neither of those units are designed specifically as a suppression platform.
3. None of those of options have the combination of being mobile, scalable, and the AOE of an actual mg unit.
4. I addressed the flak track above. It just isn't a viable unit right now, and regardless, it tends to become useless in the lategame as well (although it is more scalable than a kubel).
OKW might have the most options, but none of them are as useful as a mg. There clearly is a lack of suppression, and it seems that you haven't played enough 1s to see where the problem exists.
There's also no reason to assume there's going to be huge balance problems; this argument isn't substatial. The MG34 is already in the game, and it comes with falls. At the point where the combo of falls + mgs isn't unbalanced, then there's no reason mgs would be unbalanced outside of a doctrine. If you want to make this claim, and than explain where balance issues would arise from. It's a straw man argument to claim that I don't care about balance, when the first thing I address is the fact that OKW is underperforming.