Command Vehicles are simply Armored Cars modified to be used by a Field Commander during an ground operation. Equipped with vast radio communications so that he can send coordinate attacks and maneuvers.
In Milihime, having them in a squadron allows to perform the Pursuit Phase. Also they'll also trigger Special Tactics that will boost stats before battle.
Stat-wise, they can be compare to Light Tanks only having higher HP yet lower armor. They can also equipped with certain type of Small Caliber Guns, which allows them to destroy Light or Medium tanks.