On that note, instead of the GOP needing an autopsy, they need a bullsh*tectomy--removing the last vestiges of destructive factions (like white supremacists usually coded under the "values" / "take America back" banner) while allowing the left (as mentioned before) to swell in its arrogance and overreach (mainly cultural) to the point where the Great Left Remaking of America implodes. But that will never happen with the way the GOP fights battles today--the Cruz and Trump way, which (among several things) will never move middle road voters to even give an interested glance at Republicans.
So who should have been the GOP nominee?
Of people that actually had a realistic chance of winning the primaries, that is.
Jeb would have been the rational choice; he was not offensive, had success as governor and though his immigration statements were troubling to some of harder-core Republicans, he certainly had the potential to attract more of the Hispanic voter--now getting ready to place the crown on Hillary. Jeb's problem: he allowed Trump to draw him in. Even paying mild attention to Trump's attacks on his brother (Iraq) and his own even-tempered behavior (he let Trump turn that into a negative) transformed him into a defensive, stammering shell of himself.