According to my research (which could be wrong) these were the most produced vehicles in WWII.  I've listed those we already have in red.  The Crusader should definitely be in the game and the Bofors version would make for a nice addition to the M-16 as an allied mobile AA:
Vehicle  Country   Procuction years  # built
Jeep   USA   1941-1945   647925
M3 Personell Halftrack   USA      41000
T-34   USSR   1940-1944   34780M4 Sherman   USA   1942-1945   33403T-34-85   USSR   1944-1945   22559M3A3 Stuart   USA   1941-1942   13859SU-76   USSR   1942-1945   12671
M4 (76) Sherman   USA   1944-1945   10883M5   USA   1941-1943   8851
StuG III F-G   Germany   1942-1945   8593Valentine   Great Britan   1939-1945   8275T-70   USSR   1942-1943   8226
Pz IV F2-J   Germany   1942-1945   7394
M10 GMC   USA   1942-1943   6706T-60   USSR   1941-1942   6292
Panther   Germany   1943-1945   6132Mk VI Crusader (A15)   Great Britan   1940-1943   5300
M3 Lee/Grant   USA   1941-1943   5258
These are all the GV's with producion of over 5000 and would give a nice balance across all eras of the war and thus, all the arenas.  I gave up on this project before I got to Japan so they aren't represented but I know there's at least a couple of Japanese GV's that should be added to this list.
Sorry... didn't mean to hijack the thread.  Oh... and I bolded those I'd most like to see personally.   
