I would actually kinda like the option to say no to sex. Or maybe take it further. Let's say you romance a character that is kinda like Jack, or Isabela from Dragon Age. Someone who loves to have sex. If you opt out of having sex, and don't say the right things, they could end the relationship, because they aren't getting what they want. Want to take the romance into the next game? Okay, so long as you said the right things. But what about the third game? Are you still saying no to sex? Then maybe a consequence could come about where they cheat on you. There is possibility with this, which could make for some interesting game play, choices and role play. (Do you forgive them for sleeping with someone else, for example?)
What about characters like Liara, or Cassandra from Dragon Age? How would they react to you not wanting to have sex? I would assume these characters are a little more okay with it. So, could you have a trilogy where you romance the same character, but play as an asexual? That would be pretty good. Great for a lot of people. You are providing asexual romance options. Realistic asexual romances. I could not fault BioWare for doing something like this (unless they completely **** it up).