Well, there would've been a chance that Vermouth was Scar Akai, but unfortunately, she was seen by Gin at the same time that Scar Akai was spotted by Chianti, making your deduction impossible. I'd rather say that Scar Akai is a different BO member, perhaps Bourbon, perhaps Anokata (a theory that I fantasize about), perhaps another member that has yet to be mentioned. I do wonder why Conan was so concerned with getting Scar Akai back in the building if he knew that Okiya was the true Akai...maybe he wanted to interrogate him...