1) What are the stats on those things?
2) Epic Idea!
The mental image of a battalion of ATV sized "tanks" filled with ornery green runts barreling across the battlefield is just too good
If you do build em, definitely break out the red paint and for the love of god mod up some tank "commander" grots
Oh, and if you do go for the mods, Slap some treads on a dalek (Dr. Who baddie), give it some shiny red paint, and pop the top to have a Grot peering out.
It would be Soooo much fun to charge that one across the board while yelling "exterminate!!!!"