I really like gears in the tube, but it adds two more shafts.
Prior to the vex 2014 product unveil I was playing around to see how compact I could make a 8wd. I came up with something very similar. It would be super light without the colson wheels, but I have a hard time giving them up. I like to think of this as colsons with cleats.
One of the design constraints was cost, I wanted to avoid using hex bearings as much as possible, and actually used halved 42 tooth AM kit bot pulleys for uber cheapness.
Half live axle, half dead axle, It uses a single width of 9mm belt to power the outer wheels on the outside of the frame, while running the inside wheels on two(yes, two!) direct driven shafts. With the single 12:60 reduction it is geared for 15fps, which even on 6 cims is too fast. a 11 tooth pinion would make it a slightly more manageable 13.75 fps.
