This is not the route the Sanders campaign should be taking. It only makes things more complicated. In reality he has so much more control over the long term future of the party than Clinton does if he plays his cards right, but going about it this way will make that almost impossible.
He should drop this foolish strategy, drop the attacks on Clinton, refocus on his issues/message, and make his goal to push the party leftward and radically transform the process in which future nominees will be chosen in the future.