It won't be Schiff, Napolitano, or anyone from Mises. It would have to be someone at least somewhat mainstream, as many mainstream conservatives would be disappointed with Paul as it is. It doesn't have to be a politicians, though, as Paul provides more than enough Washington experience on his own.
That said, a Ron Paul/Steve Forbes ticket would be straight from heaven. Talk about making Obama/Biden look like little children when it came to economic issues! This would also have the effect of moving the debate toward the economy and away from foreign policy/social issues, which would please the neocons enough to vote for Ron.