As a heterosexual female I personally prefer companions with a set sexuality, but it does reduce choice of partners, and inevitably leads to complaints that the character a player wants to romance is unavailable to the character they want to play. I think it's realistic to expect to encounter characters/couples of varying sexuality in the course of the game, not so much to expect the romances explicitly to represent every possible player preference of both partner and sexuality--in a game in which the romances are a feature, not the focus of the game.
