Look noone should be locked out of content they want to experience based upon something like the race or gender of their chosen character. If someone is willing to associate with you and work along side you, chances are there are conditions under which they would consider sleeping with you. Not always, but often, that is why workplace romance and infidelity is so fucking common. Raise your hand if you have ever fucked around with a coworker without having planned it or intended to. That is reality.
I would love to see asexual characters who aren't interested in a relationship, with anyone, under any circumstances, but if a character is romanceable they should be romanceable for everyone. That is also life. Ever found yourself dating someone who wasn't on your radar?
I have worked for the same company for years and yet I have not turned Bi and considered to sleep with my same sex coworkers. And I am pretty sure that is the norm for nearly everyone. And I disagree that everyone should be able to romance everyone. That just makes them bland sex dolls. Companions should show interest in those that fits their character.