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.
