Like I said it
will end in some kind of slagfest. Anyway, any kind of attempt to include drivable tanks (I purposely exclude soft-skinned vehicles here) will be limited to a very very small thing, probably company level and below. Just to put things into perspective a german Panzer Division of 1940 fielded around 300 tanks on its own. Add to that a load of motorized/mechanized infantry (a Regiment per division), a regiment of artillery, anti-tank, pionier, signals, bridging and supply units and you're looking at a lindworm of more than a thousand vehicles. Then multiply this by 10 (for the ten Panzer Divisions the Wehrmacht had in 1940), add the Motorized Infantry Divisions and you're thinking of tens of thousands of vehicles.
This, obviously, can't be simulated. We don't even have the numbers to go beyond a company (for Germany and Britain that would be 15 tanks), and even that is already questionable (given the problems with higher player numbers on servers and the general limit of 128 players). All I could potentially envision is essentially what WoT does - putting 30 people on a map against each other. Just that we - in CloD I mean - can have AI artillery and AT-gun support as well as 88mm guns on the german side (if they're there).
One danger I see is that people won't take anything but the best armored and armed tanks, even if they were not that numerous (thinking of Mathilda and Char B1 in 1940, thinking KV and T-34 in 1941).