What do you mean about the separate char and pairing tags being synned into a lump? "Background X/Y", afaik, has always been synned to the main ship tag on AO3 (or, well, at least since the archive has actually had codified policies.) The only time it isn't done is when you're writing in a small fandom that isn't being wrangled, basically.
If you want "background X/Y" or "background char" to not get synned, you can put them in the freeform tags, and they will stay their own thing.
Alternatively, if you have a long list of background characters, you can just stick them all in one tag - "also includes Jane Thor and Betty" as one character tag - and we won't be able to syn them because they include more than one character int he same tag, so it'll stay separate.
(I agree that having minor/major character tag options would be GREAT - it is #1 suggested tagging improvement - but nothing has changed for a very long time on the rest of it.)
no subject
If you want "background X/Y" or "background char" to not get synned, you can put them in the freeform tags, and they will stay their own thing.
Alternatively, if you have a long list of background characters, you can just stick them all in one tag - "also includes Jane Thor and Betty" as one character tag - and we won't be able to syn them because they include more than one character int he same tag, so it'll stay separate.
(I agree that having minor/major character tag options would be GREAT - it is #1 suggested tagging improvement - but nothing has changed for a very long time on the rest of it.)