Two points:

"Sundered beings are unnatural and therefore bad (or worse than unsundered beings)" is fallacious reasoning, specifically an appeal to nature. Just because sundered beings are "unnatural" doesn't mean their existence is "bad" or "worse" than unsundered beings; several times the "lesser" beings of the sundered worlds have proven themselves capable where the unsundered failed. Further taken into a wider context this argument essentially condemns everything "unnatural," up to including Zodiark and the laws he wove to save the world.

Playing the "no headcanon" card means you can't argue that if the Ascians were simply allowed to see their plan to completion the world would go back to the utopian glory days of Amaurot. Nobody knows whether or not this would be the case.

Continue, if you please.