I think you guys are overrating how much loyalty Trump supporters have for him. He caught lightning in a bottle in 16 because of a weak field and the competition still playing the passive game that served McCain and Romney so well. If Cruz, Rubio, Jeb, maybe even Santorum had shown as much spine and willingness to stand up for their supporters, Trump wouldn't have even attended the convention.
I still see Trump flags flying from houses and pickups so I know there is some personality cult. I am also aware that the majority of 2020 Trump voters I'm acquainted with had to hold their nose to do it. Someone with Trump's positives and without his foul mouth, whoring, ego, tweeting, dishonesty, and various other negatives will be a much easier sell among his mostly culturally conservative voters