We have been wrestling with this since we got the challenge. Because we are concentrating on the climb aspect of the game, we want it to be safe and reliable. Two days ago we came up with a workable design. We prototyped it yesterday, and will be ordering parts from Bimba on Monday.
Let's just say that this idea has some air under it's wings

I'll show myself out.
We'll probably release a video later in the season once we have it working... hopefully.
Good luck. It's a great challenge and I can't wait to see what people come up with.