Personally, I think this idea is ridiculous. You've never known anybody that loves dogs more than I do, but I don't feel compelled to endanger my life or theirs by having 6 of them in a tractor cab with me. A tractor cab is no place for 6 dogs. A tractor cab is a place to pay attention to what you're doing; to do otherwise can have tragic results. If the constant companionship of your dogs is that important to you, I'd suggest finding another hobby.
Sorry to be so blunt, and I don't mean to be a jerk. Just telling it the way I see it.