@DrRyanSkelton The word irregular is actually quite an interesting one, because I've seen it used quite a bit where applicable. The Irregular at Magic High School aka Mahouka, irregulars in various isekai titles, and more.

Localization, when it was more honest and well-intended, did give us some great things. Like you mentioned, "Maverick" in English is a much more menacing term for something gone rogue or wrong, in this case, AI. I don't know how well "Irregular Hunter X" would have caught on in English speaking societies. The equivalent of Irregular in Japanese is likely well understood enough, or they just don't have (as many) other words/terms like English does to describe something that has gone defective.
@DarkMahesvara