Eh...Double MGs covering one another, or bunkers should shut this down. Will try when I see it next.
You don't need the entire map as Ostheer.
Already had guy using Mg's covering each other, didn't work out for him as just kept away and took the rest of the map. Also had bunkers being built with this strat but always found them before they were fully operational. Your bunker will be found while it's being built as there's so many conscripts running around meaning high chance it will get destroyed during building phase.
Also don't know what bunkers cost but any munitions and manpower you have will be used up fighting this strategy as it's literally fight after fight because it's a very aggressive strategy. The moment Conscripts stop attacking and taking is the moment this strat fails.