I would say no ... Germans should use the Panzerbusche 39 wich is the base model for the Granatebusche 39 , but instead a grenadelauncher rifle is an AT rifle .
No more uberweapons for the german side ... if they add the grenatebusche for germans should add too another weapon for the soviets , for example the mighty Ampulomet wich was largely used in Stalingrad .
I don't believe they could be carried and operated by a single man very effectively (the tube weighed 26kg, and the ammo was around 1.5kg each). We may as well add the light mortars from both sides at that point. They could be added as fixed weapons in defensive maps for the Russians though.
I really fail to understand why people seem to think the GrB 39 would be overpowered. It was a fairly common weapon available to the Germans in this time period (certainly more so than the MKb 42), and for that reason alone it should be included. I'm fairly certain it was used more often than a captured PTRS.
The Russians were simply behind in infantry anti-tank weapons throughout the war. Should the Germans be unrealistically hampered because of this? The Russians simply need to use different tactics, just like they did in the real world.
For the record, I play both sides about equally. If the Russians had a comparable AT weapon, I'd also be pushing for it to be added. But they didn't. The Russians primarily relied on artillery, air support, other tanks, and teams of two or three AT rifles working together, to take out German tanks. In an urban environment, AT grenades, and improvised explosives (including Molotov cocktails) were also used.
Two or three PTRS firing on a Panzer IV should be able to at least immobilize it fairly quickly. From there it's just a matter of using smoke, and swarming it with infantry equipped with AT grenades and explosives. Just like what was done in the real world. Does it require teamwork, and coordination? Yes it does. But is that really a bad thing?
I'm a big proponent of making the game as realistic as possible. If a weapon was commonly available, then it should be in the game (if it wasn't (ie the MKb 42) then it shouldn't), and it should behave as it did in real life. Be it rifle, tank, or what have you, it should not be artificially balanced against what the other side had. That simply is not the way it was. It should be up to the map designers to make the battle balanced.