Or simply stop the power creep and nerf the allied infatry instead, since Grenadier have already received buffs...
Allied infantry is and should be better than axis one.
Allied infantry is more expensive, needs actual macro/micro in order to buy weapons (it's not just an upgrade, you have to buy upgrades that have a considerable cost just in order to be able to buy some, then you have to add the time/micro to be somewhere near weapons racks and then only spend ammunition to buy them).
Grenadiers are just fine, they perform greatly as a standard unit; they are versatile and strong enough. This is without saying that as Ost, either in 1v1's or 4v4's, you are never supposed to win on your opponent with the same number of troops but rather use the HMG's in order to win.
That is how axis is supposed to be played, if you don't play it the way it should be played and encounter problems, the blame is on you not the game.