This paragraph is the only potential bone of contention for me. Has there been general agreement on transitioning cbook? FWIW I've read #1647 and the relevant mailing list discussion and still haven't found a definitive strategy -  personally, I think anything of that scale should be covered by a MEP with a full transition plan.

On the basis of my comments, I wonder if we are better off not pre-empting that work here, and simply removing this paragraph?