Is the goal to match ONLY the given haystack? What would be the use case? Because usually for dynamic usage you need the opposite site, find matches not the pattern. This is basically a pattern finder. Don't get me wrong, from technical level this is impressive and interesting. But I don't see a use case right now.

Well I could imagine a scenario to create test cases for your software that uses regex. But the resulting pattern is unreadable and probably not very efficient too. I don't have a better solution to this, so don't take my reply as a poison; I just analyze with interest.