I'm not a fan of Johnny, but that would have been really amusing and I can't lie and say I wouldn't be intrigued. XD Reminds me of the "sleep with Benny" option in New Vegas.
I wanted Takemura to be an option as well and was surprised to find out he wasn't. I'm playing the Corp lifepath, and I liked how their relationship developed. Takemura started out antagonistic but then they were able to find connection by the both of them being spat out and betrayed. Sure, it could just remain platonic but the basis for more is there. And besides, his white shirt with the collar open?
Someone at CDPR knew what they were doing...
Viktor would also be a nice option. I haven't finished the game but I am in Act 3, and I'm disappointed that it seems he has no friendship quests or anything, especially when he seemed really broken up over having to tell V the news. Misty could be a bittersweet option, too.