Snaqwells wroteI thought your whole reason was because we're never called "umpire." (common usage)
Not whole. As you pointed out, it can't be change for change's sake. The change has to make verbal sense (whereas "baseline" and "over the back" have proven flaws).
I don't see anything negative about "A.R.," as it's used in soccer, but it's true that there's not a lot of authority involved for a "head" referee in basketball. For some reason, it doesn't stop us from asking, colloqually, "who's the boss tonight?"
For me, it just doesn't make sense that we're continuing to use a term that is rarely used or understood outside our circle, particularly if there's a clearer alternative.