Zaion is more naturally expressive than the majority of other NijiHolo vtubers I've seen without having a 3.0, so basically just get whoever rigged her to do more work. This is kinda a crappy image I stole from 4chan but it shows a bit of how she can show a range of expressions without having any toggles.
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I mean, probably just the ones who collabed (speaking for EN only, not ID). Pomu and Kiara wanted to collab for ages and Selen's PL friends with Mumei. I don't think Alban has a deep connection with Regis but Alban is very outgoing and likes to network (people in the NijiEN /vt/ thread joke nowadays that he seems more like JP than EN because of how much he networks with them).