Just played a 1v1 as USF. Guy had MG in church on Semois. I flanked it with 4 riflemen and killed it with nades, then stole it. If that MG was any more broken though I probably would have lost the game right there.
I guess this is sarcasm but do you really think it should require 4 squads, each costing more than the mg itself, plus the additional ammo cost for grenades to counter this one cheap starter unit for ostheer? If he had a 2nd mg backing up the first one on that map your flank would probably have just been shut down immediately. Anything can work vs bad players but balance is not determined by the theoretical possibility that countering a unit is possible. Balance is achieved when the effort in countering a unit is comparable to the effort required to use a unit.
Its easy to try making this a L2P, try flanking issue but the fact is that good players anticipate a flank and focus on choke points, plant mines, and have secondary units available to break up a flank, or rely on off-map abilities like strafe. If flank execution is much more difficult and requires much more micro than preventing a flank does then balance is off.