“Cruz brings nothing to a Trump ticket”
Actually, you couldn’t be more wrong. Trumps problem is with conservatives and if enough of them refuse to vote for him in the general he could very possibly lose to Hillary.
By bringing Cruz aboard he would pull enough of them to assure his victory.
All that being said, it’s a highly unlikely scenario.
Trump does very well with most conservatives. He doesn't do so well with "checkbox conservatives" or their cousins, Shiite Conservatives...