Well I think this would be the same situation as crediting the composer instead of the singer for a song (replacing x artist with y composer on the album cover) and frankly though it may be a bit different with Vocaloid I still don't think it would make sense.
I would suggest that a format like "Lily(SeleP)-Scarlet Rose" be used instead.
I would suggest that a format like "Lily(SeleP)-Scarlet Rose" be used instead.