I look at the requirements for a scenario tank-
* must not exceed 5mph
* most of the roads and paths that the tank would roll on, are relatively flat. Most riding mowers can drive over bumpy terrain pretty easily
Riding lawnmowers are slow, easy to maneuver, low enough to the ground for good visibility, and can easily be trailered to an event.
Hmmmm I might be on to something here....
An army riding slowly yet constantly into battle. All it needs is a launcher to shoot at other tanks !!!!!