McCain's stealth conservative replacement

Clearly, the conservatives are not happy campers with John McCain as their presumptive nominee. But let's apply some Rovian logic to the equation. John McCain is an old man. Already in his seventies, there's a decent chance he could die in office, so if the Republicans nominate an ultra conservative VP from the south, the Republican base is going to turn out in droves, especially if Hillary Clinton is the nominee. They will anticipate and have wet dreams wishing for Johnny to go gentle into that good night. If, once elected, McCain proves to be healthy with no signs of failing, he can always be given the Warren Harding treatment. Once out of the way, the conservatives will have their boy. The question I don't have worked out is this: which right wing lunatic fits the bill? I'm thinking a neo con with religious right credentials and roots in the south. Must be young with little to no attachments to the Bush regime.