Recoverable anchor kit (for rappelling)

Thanks for all the replies everyone.

There are a lot of really good points presented here, and a few I think are arguable, but I'm not going to get into that.

At the end of the day the risk of rock fall, or the anchor being hung up really limits the usefulness of this concept, so I will be abandoning it. Thanks everyone who pointed this out to me. That's why I came here first!