Please don't mess up the quote function to make it seem like those are my thoughts Ptolemy.
The people that think McCain and Romney weren't conservative enough to vote for aren't a significant portion of the population in Ohio/Wisconsin/Pennsylvania/Virginia. They are largely in states the Republicans won anyways. Going farther right will just alienate more people in the battleground states that require you to win moderates and independents.
First, Romney won independents but lost because the base stayed home. If he had had even McCain's turnout from 2008, he likely would have won. And while you are right that gaining a bigger edge in the popular vote might not have swayed the electoral college math, there is still a pretty close correlation between electoral college and popular vote. So boosting the base probably would have helped flip some of those less red states. Chasing independents can be fool's gold, as Romney learned.
Second, "going farther right" is too vague to mean anything. "Going farther right" on issues like immigration will likely actually help a Republican flip rust belt states with a lot of working class whites that have traditionally gone blue, such as Michigan, Wisconsin, Ohio, and Pennsylvania.
So no, I wouldn't count Ted Cruz out. At all. I still think Rubio is the strongest candidate due to his high favorability ratings and (mostly) conservative record, but if it's Ted Cruz v Hillary Clinton, I like Cruz's chances.