I like that idea. I've got one issue with it that you should consider. The way you've placed the winch underneath, right in the center there- If you're going down hills it's gonna get squirrey. No matter what way you send it down a hill. if it gets half a whisker off straight with the pull, physics is gonna make it want to go ALL the way that direction. The ideal solution would be to place the winch at the leading edge (Traling edge, if you're letting it down hill?). A very valid solution would be to leave the winch where it is, and put a cable guide/fairlead centered on whatever edge the cable will exit the "cart" from. You "might" be far enough from the end to where you could just use an eye bolt.... Or I'm not sure if the fairlead on the winch is removable or not, but if it is, if you slid that to the (Front? Back?) of the cart, you wouldn't need one at the winch any more anyhow.