Oh, there's plenty of speed but I don't think there's enough power.
Not trying to bust up the idea, I like it, but the blades would be significantly heavier and therefore the spindel and bearing housing and deck and drive need to be hevier (stronger). all that takes a lot more power to spin and move around a yard/field. For a full size tractor, cutting grass and under brush with a mower deck is fairly light work. they have a lot of power in reserve even when dealing with a heavy Bush Hog mower.