The reason that General Mitchell's idea could well be practical is that this would be done outside the UN. Rapid deployment for the UN is an oxymoron, a big-time oxymoron. Any time you try to establish a rapid reaction force, as has been done—and R2P falls into the same category—Russia and China will veto it. Anybody who has internal problems within their own country does not want the UN to have a rapid deployment capability, so it will never happen in my lifetime.
On April 24th, 2018. See this statement in context.