true, but no one loves MC as much as vi and els do and in very different ways. it would make sense for els to take vi under her wings and as they share MC mentor her into being a capable intellegent woman. then vi would lose he childhood crush and be okay cause she would understand valentine will always be ther for her and she will be confident enough to truly live her own life, without the shadows of their past constantly weighing down on her. im sure she would visit often playing aunt to els and vals scary redheaded ninja assasin babies, and doing 3somes in the evening til vi jets off on another adventure. all speculation, but really the only other 2 who could legit throuple would be kana and val's apprentice. ines though french cant share cause she would always feel insecure compared to the other li's in a throuple. but the two fighters have similar passion and they already have a smooth and acceptable heirarchy between them... if we use porn logic instead, els kills kana cause she is the only true threat, personality wise, and she would use the rest like roman wives, as slaves and servants to prime valentine for her, and to get her off when his stamina cant keep up with her massive libido thats been held in check for way too long. also all those extra hands are needed to keep track of the scary redhead ninja babies els would be popping out like crazy. guaranteed she would be one of those insatiable pregnant ladies too, early lactation leaking every time a child cries, a river gushing whenever she catches the scent of her man working out. during his fight nights, shed likely need all the other girls to keep her from humping val in the cage at the first sight of blood. hmm what was i commentin on again? oh well im off, so many christmas vns to play this weekend, so little time, cause the family is all on break now so day hours are not my own.
I agree with where you're coming yet there's a problem in that logic: Els is a noblewoman. Yes, Noblemen usually sleep around and do whatever they want to do but there's a double standard between two genders when it comes to sexuality. Now that's nowhere near as bad as it used to be, when women were expected to keep chaste until they marry, yet it's still expected for them to stay faithful to their husbands.
Now, what you said could've been possible if they were out of the public eye, but with Valentine being an MMA fighter, that is certainly out of the question. British tabloids love harassing nobility, especially royalty. So sooner or later the cat would get out of the bag, and Els would tarnish one of the most important things in her life: Her legacy.
I honestly don't think it would make any sense for Valentine to try to pull that with Els either. Especially with someone who he sees as a little sister, who actually share so many physical attributes with Els, except the height.
I think only these throuples would make sense in this setting:
Vi-Ines: Ines may talk it into reality. Besides, although my fav girl is Els, Ines is drop dead gorgeous. Coincidentally, their facial features are very similar, to the point of Els with short, wet hair is confused with Ines by many, including myself.
Kana-Amrit: That would actually make sense with mentor-mentee situation.
Other than those, I don't think there are many throuple routes that shall exist in Unbroken.