A friend of mine designed and built a gas powered winch several years ago, before the commercial models were available. Since then, we've used it for wakeboarding/wakeskating and skiing and snowboarding in all kinds of different locations. Your idea is pretty cool, and it is awesome that you actually built a working model, but there are a couple things I notice that might be less than ideal for most people.
The biggest advantage your design has over others is the ability for you to operate it alone. To be able to do that consistently and safely (for the equipment) is something I haven't seen anywhere else. Although I have always been able to find others to join me winching, for someone who lives in a remote location, or for a high school kid who wants to skate every day in the summer, this would be a big plus.
Another upside is not having to anchor the winch, but because it takes 15 minutes to setup, this is pretty much a moot point. Anchoring our winch by rope takes a few minutes, and using the hitch adaptor my buddy built into the frame makes it easy to anchor to a truck.
The biggest disadvantage I see for you though is lack of mobility. I think I've really only used the hitch adaptor I mentioned a handful of times, because most of the places we find to use the winch (for wakeskating) you can't get to by truck. Similarly, it would be tough to get a golf cart through a snow bank to the perfect location you found for your rail setup.
The middle part of the below video is an example of a place I came across with some friends on a drive across the country. We were drove over a bridge in the middle of nowhere new mexico, and thought we'd give the river a shot. Ended up having to hike the winch down a steep bank and go quite a ways down the river before we could find a place deep and straight enough.
I'm definitely not trying to get you down on the idea, just point out some areas you can improve. Good products usually take many iterations, but the fact that you've already made the first working model means you've already taken down the hardest part.