Marriott is not in the charitable business and it won't choose the most expensive solution unless it's absolutely necessary. There exist cheaper alternatives that will keep its members whole and happy.

I'm not sure why some people still don't believe what Starwood Lurker has said on the SPG forum that unattached certificates (a.k.a. floaters) will be converted to something that's point-equivalent, not category-equivalent. And he has also said his statement was approved by the Marriott Loyalty Team.