I have to agree with Topkick. Warzone is a skirmish game, and larger vehicles would only serve as a severe detriment to Warzone's shining points, squad based combat. Battlesuits, mounted models, and *small* vehicles, such as those already in the system, are fine, but larger vehicles, such as tanks, would unbalance the game profusely.
As a note, though, I am anxiously awaiting the Jobian Cavalry...mmmm....come get some holy ass-whoopin old school....