For me, a character's ability to have free will is important and much of the A/B/O Trope takes free will away from the character's involved. Merlin in my view is a very independent person regardless of his servitude to Arthur and his duty to Destiny, so allowing him to have a choice in the matter of sex and "mating" is an important aspect of his character, and in turn how I'll write him.
I am a bit uncomfortable with dealing with gender issues, and possibly the changes to the trope I intend will be seen as a cop out. I really don't have any control (at least I don't think I do) in regards to readers interpretation of my work. The possibility of being accused of internalized misogyny again, is a risk I think that is inherent in the A/B/O Trope and one I'm willing to take.
Sex, race, religion, gender, are all areas/themes in fiction that can be difficult for writers to portray honestly without some sort of backlash. It's a sticky wicket, but being a writer who only takes the safe road or portray's the mainstream ideal rather than take on the challenge of the new, unknown, or unfamiliar does not allow for personal growth.
Best, The Nut.