I think it's a great idea, but.....
1) It's a very rudimentary design and anyone with tools and a little mechanical know how can figure it out for themselves. On the flip side, not everyone is motivated to go out and build it. That would be the market.
2) It's very costly to custom build it, which I could do, however, shipping it due to it's weight and size would make way more expensive.
3) Personal liability. I've worked in retail many, many years. I know how people are with their stuff. If abused and not used according to design, it will break. That being said, a disclaimer is not always going to prevent stupidity. Something I don't want to deal with.
4) As popular as it's become on all my other social platforms, I don't feel there is that big a market for that in reality to make it worth the time since I already have a busy life especially trying to devote it more into my personal training.
5) I could possibly draw up designs, but then again, I can easily post pictures and anyone can DIY. Trying to make money on it vs. the market on it for that 1 thing won't make or break me.
Just my thoughts. In the end, I'm more interested in making videos. I enjoy it. It's a good avenue to release some creativity and improve on it. It's a good way to promote myself in the long run when I decide I'm ready to conquer the world with my craziness.