Respectfully, I would not recommend dragging your Bravo over sand for extended periods; this will definitely cause premature wear on the very end of the keels (assuming you're dragging the boat from the front handles).
Your point has merit. I should point out that my shore where I park my boat for the season, is not beach. We used the Bravo, now a Wave, to sail over to the nice beach across the bay. Our shore has a short strip of not quiet sand, (rougher actually) but much of it is actually shore grass and/or much seaweed, making for a good slip.
That being said, after putting in a season in each boat, dragging it over the rough spots at least a couple of times a week and up onto the beaches wherever we go, I can see only a few insubstantial razor sized knicks in what is a very thick keel. Sure, it is cumulative but I can safely say that this boat will last many generations at this rate.
Your point is valid though, it all depends on the terrain.
Edit: Another cheap option...
I had some old treated 2x6's from a project and purchased some PVC pipe. I cut the PVC into short lengths and placed them into holes in the 2x6s to make a ladder like slip. I made 4 of these so you just keep moving them ahead of the boat in sequence.
I throw these into the truck whenever I'm taking the Wave anywhere. It allows me to get safely across rough surfaces, solo, if need be.
I've since seen on this board pictures of the same concept with the PVC tubing embedded into lengths or tarp instead of big clunky 2x6's. A much better idea. Wish I had seen that first.