Think about it,
Jack Olesker said if they went back to Eternia, Man At Arms will have taken over.
Emiliano Santalucia inhis fancomic homecoming also made Man at Arms a villain after he-man returned from space(it's possible he took his cue from Jack before we new about it)
Val Staples and Emiliano Santalucia made him a villain in the MVC volume 2 comics series (albeit it was an alternate universe MAA)
Dean Stefan/Ian Richter were planning on making him a villain in the MYP series
Scot Neitlich has made him a villain that gets killed in MOTUC (he took it from MYP but clearly it's an idea that he liked)
What is it about MAA that all these folks want him to do a heel run?
For me he was always the most loyal guy, sure it is a trope to have that insanely loyal character turn, but its so common that I think it would be better to be more of a nobody. Mekanek, Buzz Off, Sy-Klone, even Gwildor or Orko.
EDIT Emiliano had MAA killed before he-man's return, he didn't turn evil, I think I confused Teela 'hooking up' with King Hiss with turning MAA.