Yes, it would be cool.
Actually, the SdKfz 251 didn't use .30cal or .50cal...it was a German vehicle.
But, I get what your saying. Normally, a 7.92mm MG34, or later in the war, MG42, was placed over the drivers compartment, so that one panzergrenadier, riding in the back, could man the gun, and fire it.
Also, the SdKfz251 was fitted with the 2cm FLAK, although I doubt very much if you'd see that in the game. (Note this is just one of many weapons mounted on this vehicle.)
Later,
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34. SS-Freiwilligen-Grenadier-Division Landstorm Nederland
"Meine Ehre heißt Treue"