That looks really cool but you might want to think about using smaller wheels to make the robot lower to bring the blade closer to the ground so the bar won't go over the top of other robots? Or you could put the blade at an angle or have wedges on all sides so robots drive up into the blade.
I would be worried about using 10mm mild steel but stainless may be strong enough but you may find yourself hammering the blade back into shape after fights with vertical/drum spinners