You know, it occurred to me that at least when it comes to Mass Effect, you are always the one pursuing an LI. Why not switch it up?
Maybe I want to be chased. Maybe I want to be super tsundere and have my LI break through the cold outer shell. Maybe I want to tease them along all game only to tear their heart out in the end. Maybe I want to be the broken bird that needs fixing.
I think it could be super fun. Of course there should be an easy way to politely (or not so politely) say no early on.
That be would be great, especially if they were shady in the beginning and you didn't know if you could trust them. Being the broken bird....yes please. But don't make me say something evil if I say no.
I've never flirted with him in one of the game and that scene never happens. Even then you could have rejected him. Lesson, don't lead people on if you don't want to be ninjamanced.
Meh...I have a few characters who are terrible flirts, I especially liked flirting with Dorian and specifically told him he better not stop after his personal quest. If in real life a simple flirt meant a relationship a lot of us would be in a world of trouble. 
Anders is a damn stalker if you ask me, like a piece of sticky tape on your finger you just can't shake off. 
At least in Inquisition I could flirt with lots of folk and it was only after a while that a relationship would start, with an actual message on the screen making it clear. Hopefully that's the way they're going with ME:A. Some characters like James or Zevran or Dorian are so flirty, it's fun. Wouldn't take that away personally.
It just needs to be plainly communicated, for example I said one nice thing to Zevran in DA:O and boom, we're in a relationship. WTF? My Cousland was saving herself for Alistair to come pop her cherry (she was very innocent) so I was not happy about that at all. 