[EricH]

I only know of one team who has tried a car-style steering. I don't think it worked as well as they hoped. (And I don't remember it doing well at competition.) Personally, I think car-style is a little too complex to do on a FIRST robot.

I think that most people are going to say either 6WD with dropped center or mecanum. AndyB is right on the money there; you can practically make one right out of the kit. I'm not sure that the extra weight is enough to be a factor; at least, if you design for it to be there, you can make adjustments before building.

EDIT: I don't understand your last question. Do you mean the 8-wheel system you proposed?