Scans_Daily

I've never seen an anime or manga, set in the west that used Japanese order for western characters anyway. If anything I've seen them go a bit to far in using a person's personal name. The second Touch TV special has Uesugi on a independent baseball team in the states and all the other players are called by their first names so much that the movie didn't bother giving them last names. Despite the fact that the family name is typically what's on their jersey.

Also a lot of works set in the west already eschew most honorifics except maybe "-san," in which case they typically do use it as a stand in for Mr. or Ms. But there are exceptions.

and yes I prefer Oniisama, and Oneesama (and variants)... Except when a western character is all "Big brother," (like in Heroman).

The only problem with a case by case approach is now-a-days when Manga are often being translated in the very early stages of production it's hard to tell how important it'll end up being. Like I said the Kaguya-sama manga eschews it in official translation (despite them calling the title Kaguya-sama), and there's some direct musing on it in that scene above, and others.

But yeah in works that are heavily based on Western cultures if they still use them it's probably okay to drop 'em. Though to go to my favourite in Sakura Wars V which was set in New York they translated the non-binary and Japanese character's honorific as -san... which was pretty problematic. Since they are Japanese anyway leaving it untranslated would probably have been the best way to go.