There will be people who claim that Cruz (same with Marco Rubio, Bobby Jindal and Barack Obama) are ineligible because both parents weren't U.S. citizens when they were born. They'll shout this from the rooftops but their argument hasn't gotten much traction and little support outside of the fringe birther circus.
I predict if Cruz were to run, there might be a few angry birthers stomping their feet but there'd be no legal hurdles in regards to his eligibility that he would challenge.
If Cruz or any other person can be molded into the requirement of ‘natural born citizen’ for POTUSA as differentiated from ordinary ‘citizen’ for Congresspersons as given in the Constitution you have found a winner.