I agree with this suggestion, but I say instead of going for perks that grant these options, just have a perk that grants the options for both genders, even if the lines for each gender differ slightly. Basically, Lady Killer and Black Widow in one, without the options being restricted to the opposite six. I don't see why not. The six in Fallout is pretty subtle anyway.
To subtle in my opinion, I mean, Novally
literally slept with you

I realize a well done six scene like the first Mass Effect had wouldn't work to well in this type of game, it's not in the same cinematic art direction. But it would be nice to have some indication of what's going on.
I was working on a mod for a while and I planned to have some sixual encounters in it, here's how I was going to do it: You'd talk to the person, in this case a prosttute. The screen fades to black and the cheesiest "porm music" you've ever heard starts playing. Then the screen fades back in and the game resumes.
An entertaining and non-offensive (I'm not going on a whole six is not offensive rant again) way to portray six in a game.
Fallout 2 for example had much more sixual themes than 3 did, you could even become a pormstar for gods sake. I realise why Bethesda might want to take a more conservative stance on it from a business standpoint, and I don't blame them for it. That's how the world is today, blowing someone's head off is fine, but boobs are the work of the devil.
Still though, I'd like more sixual themes in NV if possible. If the world was destroyed like that in real life, we'd all need some stress relief.