swerve drive perhaps
really dident take that long to build 4 of them, we found these wonderful boxes that were just the right size.....
we put them under our 2008 robot and the worked great,
only about 40 pounds of pressure on them i believe, there just prototypes(our first directly driven wheel) we have other more powerful motors that we could switch them out for quickly if they dont hold up, only six motors used total(4 for driving wheels and two for turning them)
as for the wires,thats something we'll have to figure out later
ps.. it may or may not be, based off your cad you posted awhile back.....