Been playing USF quite a lot recently to see if these balance concerns were true, indeed they are, open double mortar into 2 RE into captain into stuart.
^ Most braindead, microless and superbly effective opening i know currently for ALL factions ( in comparison )
Is that about 1v1 mode? Not really a 1v1 player, but I'm sure it won't work against decent Wehrmacht player.
Your opponent will get better map control while you are sitting on 2 mortars and you won't see Stuart anytime soon. Instead there will be 444 which will rekt your REs, mortats and probably Cpt too.
In 2v2 this may work if you will be supported by your teammate.
In 4v4 it won't work, because once your mortars will be pushed out by Kubels/SPios/Volks/Grens you'll lose fuel point on your "lane" and won't get it back anytime soon because of long retreat path, so again no Stuart rush. REs just won't cut it.