I think the tradeoff point, where having set sexualities isn't too limiting on romance options, is at >8 companions. With 4 men and 4 women:
- 1 of each can be straight
- 1 of each can be gay
- 2 of each can be bi
This would allow for any player to romance 6 companions (3 if you refuse to be e.g, in a gay relationship). Maybe 1 or 2 fewer if certain companions have race/religious restrictions, like SH maybe not being willing to romance a cleric of Selune.
All you would get in this scenario is "I wish the male hetero companion was more this" and "I wish the female bi companion was more that".
I agree with the posters who have said the writing is the problem rather than the sexuality per se. A companion gives you the glad eye and you say "yay" - you can then take it as far as you want or the game will allow. If you say "nay" then that is the end of it.
Or you could all just go and play the Sims. I wonder if there are people in Sims fora bemoaning the lack of sneak attacks.