I have no doubt that Trump will change his positions on issues instantaneously and without the slightest indication of discomfort, as he has already done many times. But I do not think fundamental character traits can easily be faked, particularly by someone so obviously in thrall to powerful infantile needs and fantasies.
As many observers have noted, Trump is obsessed with anxieties about masculinity, dominance over male competitors, and sexual prowess with "trophy" women [witness his inability to let go of the issue of his small hands.] I think it will drive him utterly out of control to be locked for months in a contest with a strong woman [and say what you will about Clinton, as I already have, she is indeed strong.] I can easily imagine him doing something insanely self-defeating, like manufacturing an excuse to pull out of a scheduled presidential debate.