Honestly, that's what i'm most interested in atm, who is gonna be the mc of the love route?
Tenzin, Bumi, Kai, or Zaheer
Tenzin would be the easiest since he already wrote the scenes for him and the female cast. Only minor updates would need to be included if he wants to go back and add scenes. That way the love route can feel twice as big because it will have the old sex scenes, and the new ones he wants to work on.
Assuming he wants to only have scenes with the new women (Opal, Suyin, Kuvira, Kya, etc) then I'd put my money on Kai or Tenzin again. Bumi seems like he'd be an NPC in that universe, like Iroh in book 3. Zaheer is an enemy who wouldn't be able to interact with most of these women unless it was a slave route. Kai would be interesting, like Aang in book 1.
Tenzin would still be the easiest, given how much of his dynamic was already established in the slave route. Tenzin could be rebuilding the air nation and his training sessions would be how the avatar trains. So he could have a mission early on to Suyin's base and see Suyin, Opal, and even Toph and Lin. His base would still be air temple island so Pema and Jinora scenes are still available. Kya could stop by on the island. The Red Lotus could be the main threat, so that gives you interactions with Ming Hua and P"li. They could even have something like that time Tenzin got his ass beat by the Red Lotus as a moment where you have to improve your bending. And Kuvira could be the crazy girl that works for Suyin since she isn't a dictator yet.
Even Tenzin's relationship to Korra makes more sense this way. When he first met Korra, she was impulsive so putting her in her place fit with the slave route. After harmonic convergence, Korra would have had time to get to know Tenzin, become more likable as a person, and even develop a crush on him.
I just remembered that MITY is already writing the love route. So these aren't suggestions, this is going to be my prediction.
