I am not entirely certain we can rule Q himself out as a suspect?
It would certainly seem to be someone with knowledge of Q.
It actually being Q is kind of the double-bluff. But while obviously nothing's impossible, I'd struggle to see why someone who regularly shares a bed with Kanti would choose to use Pink Clouds on her in her car in a more or less public place. And using Kanti doesn't really put any distance between him and the crime; he might as well go and get the women himself.
The people I think we know to have some history with Q: Jacqui, Miriam, Yves, Sawyer (and Hans), and possibly Katie, and now Giselle too. Anyone else? I think Laura is too unlikely. I don't know whether we can rule out the Vik/Julian/Cherry mix.