You write:
So far I have received six comments on the proposed sign-or-delay system, two in public, four in private. All have been supportive of concept, but there have been specific technical issues with it.
I think you are reading those replies through rose-colored glasses. They were politely telling you "no way."
The real goal of this plan is to change the software infrastructure so that crypto can easily be inserted.
Please keep in mind that it is impolite to _impose_ your beliefs on others, and to punish people that don't believe as you do. That's what certain governments that people on the list are concerned about do. People don't respond well when forced. All you will do is alienate them. I suggest you offer an incentive for signature use rather than a penalty for non-use. For example, the "Quarterly Cookie Quota" (QCQ), a pledge to send a package of cookies (good ones, too) to a signer picked at random. This will cost you $100 a year, less than the time/$ cost of modifying the mail list software. Bottom line: Use Carrots, not Sticks. Using sticks is counterproductive, especially when you try and use them on ornery jerks like the membership of this list (humble correspondent included in that characterization).