I once had an idea about hard mounting a Bike seat in a wagon to tow a Steadicam camera operator around using a bike (slow speed of course), but I never could find the right platform to pull it off. Today Jerry shares a find on some Marine Grade aluminum folding carts that could be used for a variety of things besides just hauling gear.
The heavy duty folding Aluminum cart's large 20" airless, foam-filled rubber tires are designed for easy maneuverability and stability on rough or thorny terrain as well as on steep grades, and will never go flat. The cart is designed with a capacity of 5.75 cu ft moving up to 330 lbs. If you want a fully enclosed unit, there is an optional gate. If you plan to tow the cart with a bike, there's also a trailer hitch available. This might be my solution. [Thanks Jerry]