@Randal'Thor (sorry slow reply, missed the notification) I don't think we need to worry about "policing" at all. Nor do we need to create a list of puzzles. Users would just nominate their own puzzles (as they currently do) and edit them into the list. Whatever ends up is there is "valid", via self assessment.

Agree with you on Option 3 though. Feels a bit like a compromise that brings the worst of both worlds.

On option 2, I do agree with your assessment/hope that people will be spurred to creativity by a strict restriction, but it seems like most are leaning towards option 1 at this stage. So maybe once we see how it goes, we just propose follow up challenges with specific pairs.