Something to consider is wheel size. The baby joggers use a pneumatic tire of a size that deals
with bumps & obstructions far better than hard rubber wheels.
Another advantage is the tricycle format. It's a lot easier to deal with than either two OR four wheeled carts
If you don't think the fabric seat is sturdy enough, it shouldn't be a problem to make of have made
a metal frame.
There was a cart sometime back maybe in LFF from the hunting side that had 2 large wheels and could be used to transport game that had been shot. Don't guess anyone here has a link to it?
I purchased a 2-wheel wheelbarrow from the hardware store. I didn't mount the container but made a platform out of plywood. Just kind of threw it together pretty fast so I could haul my 8X10 gear off into the woods. I use tie-down straps to keep everything in place. It was only about $40.
I do a lot of location video and photography - my kids got me a rock-n-roller cart for christmas a year back. Freaking love it, used to use a big steel dolly, but these carts are so cool, and fold down very small when not in use, or in a vehicle. And lots of accessories to customize. May not be just the thing for the OP but they're well thought out and really handy. They start at $100 - Dead Link Removed