I hope that the R's don't screw with the nominating or convention rules and it plays out how it plays out. If they fail to pick either Trump or Cruz, that will be the end of the party.
If Trump does win the nomination (and hopefully the election), that he names Cruz or Abbot to the USSC. As far as finding a running mate for Trump. He'd be smart to pick a fairly conservative Governor or former Governor. (Jim Edgar from Illinois or Mitch Daniels of Indiana as examples. It is a shame that John Nance Garner is not available.)
Cruz, if he is the eventual nominee would do well to pick a current or former Governor. Christie, Bush, Jindal, Kaisich and Rick Perry being off the table. Sadly, whoever the nominee is will have to play the diversity game in naming a running mate. I could see Trump naming Palin as his running mate. I don't see either as pulling someone out of the senate, although Trump naming either McCain, McConnell, Ryan, or Lindsey Graham as his #2 is not out of the realm of possibility, he will need someone to help him on the legislative side of things and doing what Kennedy did with Johnson, does make some sense.