How much interest would you want before setting sail? For the first chain you have Jeremy and yourself, and maybe me (if I can solve one of the puzzles, that is) or others.
Also, I see that there is no requirement for puzzle-creation time for the subsequent chain puzzles. Do you want to set a limit, say 2 weeks, that is the maximum amount of time for creation?
The downside I see is that later puzzles, with more constraints, will take longer to make well.
But if there is no limit, then a chain could go without another puzzle for months, which would be Very Bad.