The idea I posted above would simply clamp to a pair of Cat Trax. It would be more like an acessory.

My friend Ralf Cole runs Bradenton Beach Boat Rentals. Two tornados in one week played havok amongst his little fleet of G-Cats and he's in the process of putting them back together and getting the hulls painted with white Imron. I keep my G-Cat a few miles north of his place, but still right on the beach. I've been having toughts of putting a 5HP engine on a tricyle with floatation tires to run around on the beach for fun and pull my boat and some skimboarders.
(But I could get in a lot of trouble for doing that )