To me it's as simple as this: every character should be severely disappointed by any type of cheating. They've established this for all of them with the exception of Halsin and Halsin should be rewritten to have his romance start after he frees Thaniel and you convinced Oliver.
Mizora, drows, Emperor, Haarlep all should lead to a -50 approval at best, breakup at worst. You get a pleasurable scene (or some text in the case of drows), your love interest is pissed, what's not to be expected, they've all written to be mono by act 2 and by act 3 are very much yours and you theirs. Personal story choices determine the outcome of the romance otherwise, not these optional scenes, they should just anger them or cause them to break up with you.
I still don't really understand how all of this got a pass when the writing otherwise has been done so wonderfully.
