The problem is that if you feel that you need to react specifically to a certain faction, i'm sorry but then you have a bias towards that faction...
...The problem is lying to yourself about not been biased.
I'm loving every word here - a psychological approch to balance
But to the point - I would react to a lot more of balance threads, but on this forum there is not much need to sort of "defend" USF/SOV/UK/OKW. They have their crutch units and the answer to posts reducing their crutch role usually ends up in stuff like: adapt, it has to be like, you have combined arms (as if aothers didn't), then come more philosophical arguments: it is the game design, this unit is not supposed to to that, etc. And although there are solid, logical, unbiased arguments that some units overperform the person posting them is just treated badly by some forum members. A good example would be the scott or pack howie. They have been 2 shooting those poor 4 men squads for a very long time until people finally admitted the obvious and done sth about it. Funnily enough, a few weeks later we get better vanilla rifles, which, to a large extend, hamper the use of assault grens for ost (the only early units that could mop up the pinned squads early on providing some breathing room for ost at that stage of the game). And again forum members don't seem to even see that (apart from 1 member I think), but are only concentrating on the fact that they were smashing regular grens anyway at medium-close so if they are even stronger now it is not a problem (It's so ridiculous that even difficult to comment). Don't you see the damage to the overall balance? Allies who play against 2 factions only anyway, will play again against 1 in 1v1 if the opponent is of similiar skill. To top it all, some people allegedly watch replays by Dane/tightrope etc and don't even seem to notice that a lot of players try not to use grens at all. If they do they respond that this is how U adapt - by not using yuour mainline infantry (incredible).
So coming back more to the core of the thread: In my opinion, putting all psychology behind, I really believe that grens should be somehow buffed to keep up with the buffed cons and apparently rifles. I'd go for more utility such as sandbags to surprise the opponent with positioning and make them spot more before assaults. Grens don't have close range nades anyway so after closing in allied squads could just win easily. It wouldn't be a great balance change (contrary to what you wrote) but a slight response to more powerful vanilla rifles and 7 man conscripts. In my opinion, it wouldn't change much. I like your bunker idea still, but I;m afraid that spending manpower in ored to equalize the matchup might be a move in the wrong direction. Unless what you meant was sort of sit in a bunker instead of behind sandbags. I feel it could be more difficult to balance though than those sandbags.