[magnets]

I'm not sure that the 3/8" belt is strong enough to power the drive, and I would also stay away from the lazy susan bearing. The lazy susan is able to withstand the thrust loading, but it will have trouble when there is any amount of side load. I would recommend putting another bearing for the module rotation above the steering pulley. Also, I can't tell what sort of bearing you're using for the shaft with the miter gears, but it should probably be a thrust bearing because the miter gears will try to move away from each other.

While it probably is possible to make this module out of a bent sheet of aluminum, I would recommend against it, as it will make the corner too thin.
It would be easier to make the top plate a separate part, then put some holes in the side, and bolt the side plates on. I know that 1640 did this, as well as 118 in in 08.

Another question, how does the tube that sticks out of the top plate get held on? Is it welded, or is it something else?