Actually, Jäger, Stormtroopers and Panzergrenadiere all use the same model! There's just two different skins for it.
As for the Panzer III, I don't think there's a model, just several attribute files. It's the same with the M2 60mm mortar, I think. There's a working M1 81mm mortar, though! The M1919A4 has a model, but it looks pretty bad.
Skins? Huh, so that's why they looked the same in the Editor, I was kinda confused about that, heh, lazy Relic.
And yeah I know about those, as I said I have only see the 50mm gun that was supposed to be on it, as well as the models of the M1919A4 and M2 60mm mortar, the M1 was in Ardenness Assault.
But that video sheds more light on what could have been tho, especially for the OKW since most of the stuff mentioned there is basically already in game but not used, as far as the Wehrmacht goes... a few of the abilities and units are from the Urban Assault, I've never heard of the others, well, except for the Panzer III of course. Oh yeah and the Soviets with their Not One Step back commander.
Interestingly enough there were planned combat groups like in CoH where you would get random vehicles and infantry units, those were fun to use when you had the man power for them and went Infantry Company.