John Deere makes a 24" diameter x 72" wide rotary brush that mounts on
the front of their gator and is powered by a 10HP motor. It might give
you some ideas. If you go with a large rotary broom concept it will
need to be mounted to something because it would certainly out power
you manually.

Black and Decker, Toro, and others sell "power brooms" that are smaller
and can be handled manually; but it sounds like you want something more
like the "rotary brooms", which are much larger.