[Tristan Lall]

To operate them together, just gear or chain them all together. (It's that simple.) You could do two kitbot transmissions chained to sprockets on each side of the wheel, for example.

Well, it's almost that simple. You can assume that they'll all spin at approximately the same speed, out of the box, certainly close enough for your purposes. Perhaps the only real pitfall is getting the polarity or PWM backward on some of the motors—you can probably guess the result.

Those considerations aside, you've already heard a few responses discouraging the idea. Let me expand on the reasons:

You have a ton of power at that one wheel; if, however, that wheel isn't in contact with the ground, you can't move.

Also, since the traction of that wheel is going to depend on the amount of weight acting on it, you want to support your robot entirely on driving wheels (if possible), so that you're not wasting any of the robot's weight. It's a waste, because your pushing ability is a function of the traction—so in essence, if you divide your weight among several contact points, and only one is powered, you're going to divide your pushing ability by a similar proportion.

Now, you've got to also steer somehow. Traditionally, robots steer by varying the speeds of their wheels—obviously you can't do this. You'd have to implement some other form of steering, like Ackerman (car) steering, or actuating brakes on the wheels located on the inside of the curved path that the robot follows (somewhat like a tank). Actually, the best method here is probably to design a large swerve module, mount everything inside of it, and put it in the middle of the robot. For various mechanical reasons, none of these are very practical.

Basically, compared to a 4WD, wide-tracked kit frame with kit transmissions, all of these 1WD ideas pale in comparison. I've heard that there's no such thing as a bad idea; well, whoever said it was wrong—this is a bad idea. But that's not to say that the thought process involved was a bad one; in fact, I commend you for thinking outside of the box, and putting serious consideration into the matter. But just this once, I'd urge you not to try to implement this on a competition robot, unless you take masochistic pleasure in dealing with your robot as it experiences the problems listed above.