ST should never be in the game in the first place.
The whole principle the unit is build around does not fit CoH spirit series.
I agree with you, for once.
I think the AVRE could very easily and convincingly be turned into a Brummbar/105 type unit, though I really don't know how you could change the Sturmtiger and have it still feel as though it's acting "correctly". Both units really should be changed though, oneshot abilities like them (and the old B4) are abhorrent design, and do not fit CoH2's gameplay loop.
On topic for OKW commanders: Scavenge clearly needs a rework, you're almost always better served by picking Overwatch, it really doesn't provide anything terribly unique or interesting (Though the Ostwind is a fantastic unit). Beutepanzer have been suggested before: Some sort of Beutepanzer Sherman (Some type of command tank?) may be an interesting avenue to explore.
GoD and Luftwaffe similarly could do with some tweaks, though they're seemingly not too unpopular. I'm not sure what you might do with GoD, but I wouldn't mind seeing Fallschirmjager tweaked to have a more defined role (Even if that results in them being made worse at some ranges) so that the commander doesn't crutch so hard on them. This might leave room for a "Luftwaffe Ground Forces" squad of some description, or the commonly requested Ostwind.
Other than that;, as Sanders has said; OKW's commander selection is fairly healthy, seemingly. I'd LIKE to see changes to Elite Armoured, but the numbers imply it is pretty well balanced.