Another primary consideration in introduction & eventual disappearance of Segmentata?

[Flavivs Aetivs]

his lackeys Avitus and Majorian

Ah, so you don't hold with Gibbon's idea that Majorian was "a great and heroic character, such as sometimes arise, in a degenerate age, to vindicate the honour of the human species"?

I wouldn't call it a degenerate age at all, but Majorian I see in a very positive light based on the facts. I'm disappointed that Aetius had maneuvered to have him removed in 452 rather than support his position as heir to the Theodosian throne, but Aetius also may have known Majorian would be a pawn for whomever succeeded him (Aetius) in that position (manager of the pars occidentis).