Here's the thing: If McMullin carries Utah, that's 6 EV at his disposal. This is critical because if Trump wins, he's likely to do so with just over 270 EV. McMullin is not really an "Independent", but a #NeverTrump movement conservative Republican in the Ben Sasse mold, and he's got an agenda; to put a "Constitutional Conservative" in the White House.
McMullin probably has personal control of the six (6) folks who would serve as his electors. If he carries Utah, he could have them vote for himself, in which case the House would likely elect Trump, barring massive changes that would allow Hillary to win.
Utah has no laws against faithless electors, so that shouldn't be a problem. I'd imagine that even though the ballots have Nathan Johnson as VP, Utah's McMullin electors would vote for Mindy Finn for VP.
Really it comes down to "what is a faithless elector"? Is it someone who voted against the will of the people or the will of the candidate that they are pledged to?
There haven't been that many applicable instances of "free electors" (discounting 1960). In 1912, Taft's electors chose an alternate VP since Taft's died (not that it mattered). 1872 was a mess and so far back that there might not have been any applicable laws.
Basically, all I'm saying is that it would be completely legal for the McMullin electors to vote for someone else.
