Yes well but what if your uhh "donkey" gets 'is "thing" caught in the toothed wheel?
= donkey sausage
-all in fun.
More serious questions:
Could a finger get caught in this mechanism that carries the whole load of the kite?
In the picture the line appears routed so the part wound by the thumbwheel runs past the standing part of the line (part going up twd kite). This looks like it could foul in a slack line situation. Could it?
What's done to prevent overrides on the drum that the line is wound up on?
Would it be better to wind a strap than a line?
Could the thumbwheel itself foul the standing part of the line? Looks close in the sketch.
Maybe you have thought of all this stuff and more.
Sorry to be such a critic, I am in the middle of designing and building a small boat now and every component I design, I find I am looking for the most robust, cheapest and lightest (when I can afford it) solution. Which usually also means the simplest. It is often a copy of some idea that has been around forever, but the payoff is it's more likely to work and usually takes less time to build. And sometimes you don't have to do as much math!
So I have grudgingly come to have more respect for KISS than before...
If you have a pull-pull system with balls to grab, maybe that's the problem. Your idea could be a great solution, but so could replacing the pull-pull rig with an old fashioned ladderlock push-pull strap or a rope and cleat system. No solution fits everybody.
I do think the idea has potential, but marketability might be elusive given the need for a new QR spreader bar to go with each unit. Slingshot charge over $100 for theirs....
Anyway, show some pics if you make one. Be cool to see it.