alphashitlord said:
I was gonna say we could do what was done with Zen's alt forms but with Vei having the _(vtuber) qualifier on top of that you might have a point, on the other hand I agree with Rodent that (bikini) can also work as an alias.
Given the fact that evazion himself has questioned how Zen's tags are currently organized in the past (forum #257164), one could question how things might square out on that front, making her situation not one to be emulated.
Regardless, whichever you go with, whether summer or bikini, I think pairing that with the year just makes sense for simplicity's sake (so, (bikini_2021) and (bikini_2022) respectively). I just personally prefer 'summer' be used here because neither costume is purely a bikini. The former has short shorts and a crop top, and the latter has short shorts and a camisole. It's the same reason why I argued for Houshou Marine (Summer) and Hakui Koyori (Summer) to be qualified as such (forum #252628, forum #357928).
On a similar note, I hesitate on supporting renaming her 4th costume because it serves as her Live2D default since her VShojo redebut, and we've left the question on how to handle defaults unresolved for now because if we start deciding for one we start deciding for all of them.