At the top level, I dont think you have the luxury of switching crews anymore. Just too hard to keep both crews in tune with yourself and the skill level needed. As most teams are professional sailors, financing would be harder. And finally, how would you motivate your heavy weather crew for the full olympic cycle?
Today, the class rules in the Tornado class dont say anything about the qualification process, that is fully up to ISAF and the national assocs(MNA). If they decide that Bundys best chance at winning is with the australian prime minister, that is his crew (or could the queen represent Australia?) <img src="http://www.catsailor.com/forums/images/graemlins/grin.gif" alt="" />
There is even no warranty for the team who qualifies their country that they will get the olympic berth. It is all about winning (and IOC's money)