Here's a worthwhile thought experiment. Ignore your personal feelings about who you'd like to see as a nominee and running mate. The point is to objectively analyze a perhaps not-so-outlandish scenario that might unfold in this time of seismic political party re-alignment.
Suppose that Trump got the GOP nomination (which appears most likely), and sensing the great need to turn many blue states red, he chooses Bernie as his running-mate. Bernie accepts, having lost the Dem nomination and resenting the corruption in the Dem nominating process.
Then suppose that Hillary gets the nomination on the Dem side (most likely), and sensing the shifting red-blue map against a Trump-Sanders ticket, she chooses Cruz as her running mate. Cruz, stinging from losing the GOP nomination, accepts in order to keep the #NeverTrump spirit alive all the way to voting day.
1) Discuss the similarities that would link Trump and Sanders together, and those that would link Clinton and Cruz together. How much coherence would the Trump-Sanders campaign have in the fall of 2016, and how much coherence would the Clinton-Cruz campaign have?
2) What would most greatly distinguish the two campaigns, in other words what would be the greatest fault-lines in the general election?
3) Which campaign does best with which demographic groups?
4) More importantly, which campaign takes which states? And therefore, which one wins the election? You can be general or specific (play around with the 270 to win site).
Again, this isn't fantasy football. This is an exercise in surveying the state of party politics during a period of great re-alignment. I'll post my own thoughts later in the comments.