Seems to me this is a case where "put up or shut up" might apply - we can test this theory without any centralized action at all.
I *think* the matter of making 2 lists (or 3, or 4, or...) can be done in about 1 hour using Procmail and Mailman on an Unix box: subscribe once to the ietf-announce list, let procmail feed into a set of mailman aliases. Go. Anyone can set up this without any help from the secretariat. If it gathers 10% of the subscribers of the announce list itself, it has proved itself in the "marketplace", and we can think about letting the Secretariat run the service. Anyone who wants to put up? Harald