Thanks for the interest and kind words. No worries, the MC is a dom type, even when he's a nice guy, so he'll continue to "wear the pants." Well, until it's time to take the pants off.
I think you'll be happy with how Nicki's relationship with the MC develops. Not to give anything away, but you're definitely onto something. Logistically.. it would be very difficult to keep Nicki in the story, when she's an utter wreck of a human being, constantly humiliated and beaten down by the MC. And it wouldn't be very fun to write. The MC mentions her pluck and sass in the first chapter, and over time we'll see that quality emerge.
But, I'll also say this - people are thinking of the game as built on "routes" - which is kind of correct, especially at this juncture. But really, what I'm trying to do is develop a story that relies on a rudimentary point system, which will be steadily altering your game as it continues. As you play, you accumulate points for the girls, as well as "dark points," for the MC, which will open or close certain dialogue options, choices, and narrative descriptions.
A character who has a dark point rating of 6, for instance (which you earn by playing the "bad" route in Chapter One) won't see the world in the same way as a character with a point value of 3, or 0. So, if you were a good boy in the first chapter, upon meeting Gabby you might think, "Wow, she's cute! What a little body on her.." while a bad guy might think, "Fuck, if we were alone I'd put a leash on that collar and make her howl.."
Now, that said - even a good guy can choose to make mean decisions when meeting a new girl, and vice versa. Your MC might think Nicki is a money-grubbing whore, and Gabby is a sweet kid. Or that Nicki is a cherished friend, and Gabby is a snotty little punk who needs a cock down her throat. As you accumulate points with the girls, this can begin to alter scenes in interesting ways. I'm writing a scene right now where two of the love interests meet, and their interactions with one another change based on whether both like you, both hate you, or one likes you and one hates you. Makes for a really interesting dynamic!
Also, you do have the option to be nicer (or meaner) to most of the girls, as you progress through the game. The next time you see Nicki, if you were a monster to her the first time, that will obviously color your interaction with her, and how she sees you. But, you'll also have the option to be kinder, which might realign your relationship to be less hostile.