Personally I think I'm essentially neutral in the 'defined sexuality' vs 'playersexuality' of characters, since I think it essentially comes down to a trade-off of realism vs player freedom. I might lean more on the side of player freedom, but it's not as if I don't love plenty of games with gated romances (and let's face it, if they did gate some romances, someone's just going to mod the gate away within a month anyway...).
What I would like to see, though, are some actual flirtation options in pre-party dialogue, so my character can perhaps intentionally trigger romance options with the character(s) they might be interested in, instead of having the entire camp suddenly be horny/jealous over them when you get to that scene. Because really, while that's funny for my warlock who would if given the chance flirt with everything that moves, it's going to look a tiny bit nonsensical when I'm playing my socially awkward wizard who definitely wouldn't have given the entire party that impression. It would also rescue the people who felt uncomfortable with certain characters coming on to their PC by making it the player's decision to initiate rather than the companion's decision.