In the end, it's still a game, and to be fair to all players, I think a game that offers a romance system should either have all characters being completely player-sexual or all of them should come with a set preference. I'd prefer the first option though, as that adds lot of choices for every player. Or if we just stick with the narrative and characterization, then we would need some companions to be 100% straight or another one to be likely homosexual.