I would 100% support implementation of prefferences for our companions ... but it should be set by character, never by Player. :-/
I mean, Dorian (DA:I) was great character and i loved interaction with him, even tho im regular heterosexual male and never feel any atraction towards him ...
But imagine he would turn straight, just bcs player picked something when created his character? :-/ That would ruin it whole.

I dare to say that some dialogue option "
Im not interested in fe/males" in conversation with any of them, that will block out proposions from others of same gender ... should be suficient in my opinion. :-/
I mean, our companions knows about everything else that happened in camp imedialty, and they are judjing ... so, what is the harm here?