The VP is often the most trusted adviser of the President. I don't want Rand being softened up by his VP like George H.W. Bush did with Reagan.
If necessary, Rand could pick Mike Lee as he does not come off as combative like other choices do. His voice rings reasonableness.
I doubt Joe Biden is Obama's most trusted adviser. He picked him solely to appeal to white middle class voters (especially the pissed off Clinton supporters).