I have a 4 WD Dakota with a shell on it just for that purpose. Then several of the fields I play at decided not to allow any NEW vehicle based tanks. Just grandfathered in tanks already built. It is for sale. $1500. Street legal. Thought I would just pop the shell off between games and drive it4 miles to work.
Many fields are wanting to move to lighter, less powerful vehicles. The vehicles used are often near junkers or are junkers that still run. Mechanically marginal and that is what the fields are worried about. A ATV with a stuck throttle or failed brakes running into a plywood bunker vs a Dodge Dakota is a whole different outcome..
In addition, many players are beginiing to understand that bigger is not better in paintball tanks. They are just bigger targets that are easier to eliminate.
Many fields can develop tank roads for a golf cart sized tank for a fraction of the cost than building tank roads for full sized vehicles. So much easier to brush hog between trees than to bulldoze trees. Creek and ravine crossings again much easier to build for lighter and smaller vehicles.
Besides the expense of building and maintaining a vehicle based tank, they often require the expense of a heavy duty trailer and a rather expensive tow vehicle to get it to the games.. If you drive your tank to a game with turret, cannon, and machine guns in place, you will get stopped by the police in every jurisdiction you drive through. Too many cell phone in the hands of patriots that have never heard of a paintball tank.
So LOTS of reason why we see smaller and lighter vehicles used for paintball tanks.