Have you actually done Isis route? Her domination variables are actually the exact opposite and she actually gets turned on by the mc dominating her on their wedding night. The variables are for the mc dominating her not the other way around. Isis is also unlikely to harm Elis in any way as that would undermine her own authority. Isis has her own goals but she seems very unlikely to act against the mc. Seems more like her goal is actually to prop him up as she wants to be empress
I have tried it yes, a couple of times or so. And I personally just don't see why I would ever pick her over Aurora now, on any of my playthroughs. You even admit that the only reason she wouldn't act against the MC, at least right now. Is because she wants to "prop him up" and use him to be an empress. Doesn't seem very trustworthy if that's the case IMO. If things ever go bad enough in the story, I could 100% see her dropping him like a box of rocks and turning on him if a better offer should arise.
Say a hypothetical scenario happens, of Conrad trying to take the throne. I could see her being swayed to side with him, if she thinks it's a done deal for him and she will get something good out of it. Aurora on the other hand, I see as being a rather "loyal until the end" kind of wife.
Also I just find Aurora to be very boring and plain Jane. I don't really find her attractive and her personality is very boring and passive with a lot of her scenes coming off almost rapey as a result. She has no goal or motivation and is even outright afraid of the mc depending on what you do. Just a very boring uninteresting character
I find her to be more attractive in general, and less of a giant pain in the ass. And I disagree fully about the "plain jane" thing. She's pretty fucking beautiful IMO. She's got that icy pale skin, blonde look, down to the tee. I usually don't go for that, but it just works with her really well. Also, I don't need her to be just another complex plotting woman in this game, thank you. Already have enough of those. She gives a nice contrast to them actually. She reminds me a lot of Catelyn Stark, whereas a lot of the other women in this game (Isis especially) give off Cersei/Margaery/Arianne vibes. Just more trouble than they're worth. Whereas Aurora, is just a sweet honourable woman who will try her best to be a good loyal wife and mother. What else could you want from a partner honestly.