We (357) stuck with our mechanum wheels this year but used 9 rollers per wheel instead of 6, redesigned the rollers to have a hard inner core for durability and a soft outer layer for traction, and also mounted one set of the wheels on a pivot to make sure that all four wheel came in contact with the ground at all times. Our record this year so far is 16-4-0, and the modifications really helped achieve that.
I gues my vote is that if you can make it better, go for it.