A minor point: according to the proposal, "There will be a two week grace period ... for groups to claim their existing RFCs. After the two weeks the remaining RFCs will be closed". Phabricator RFC tasks represent ideas, not RFC processes (in theory the two could have separate tasks, in practice it is rarely done); those tasks are usually the result of a significant effort to understand, discuss, develop and document some idea or proposal. Tasks representing ideas should not be closed unless the idea itself is found incorrect, implausible or disadvantageous; it makes them hard to find for future discussions, and it is disrespectful to the contributors who have spent their time developing those ideas.
This is not to say that the unclaimed RFCs shouldn't be closed, and removed from the decisionmaking process; but please, find a way of doing it that doesn't require closing the Phabricator task (or split the RFC and idea into separate tasks).