Questionable Questing

I like the civil war and different interpertations of the same god, some real interesting world building and to be honest in classic dnd Drow society was never that consistent so starting with a sort of fresh palate is a pretty good idea. Although a fun story idea would be the full unrepentant evil femdom BDSM slave owning drow's invading a normal Westros and just seeing their reaction would be priceless.

But sure I would love to talk Kachan. I kind of need a way to endear him to an audience that's pretty prepared to hate him since he's going to be a major plot point soon.

First, amplify the sexual tension with Deku by a thousand. Second, have the players through Robbin see a connection.
Did Robbin know how to be good? Did anyone show her? Kachan remindes her of not knowing how to be decent

Smut wise, Kachan is a bully. Use the unique personality. Don't have them just make kachan a soft submissive. A brutal futa Amazon enforcer. A sadistic and taunting femboy alpha bitch.

Exploit his ruthlness as a weapon for Robbin

That's a pretty good idea actually. Robin was raised by the matron of a brothel. It's where she got the obsession with sounding educated, you've probably noticed the use of deliberately longer and pretentious words, the need for control and looking beautiful all the time, and not necessarily being rich, but being seen as sophisticated and interesting. Robin hates being ignored more than anything.

Basically she was taught all the skills on how to fake being a person, and it was only later after Robin met Lucy that she realized she didn't have anything underneath all that.

Funny enough the thing that made Robin start to regret being an assassin isn't because she felt guilty, but because she realized how boring it made her. She didn't have any hobbies, any friends, family, favorite restaurants or places to visit. Everything was centered around traveling, training, and preparing for the job. She was a two dimensional character wishing she could be more.

She sees in Kachan someone with the same dominating sexual desire and the two dimensionality. A prisoner of his nature, not aware of how bad he us at being a hero. And then there's the Deku thing.

Make it weird and sexual and very in denial. Kachan wants to fuck Ochako so he can then fuck Deku

Also possibly he wants to femboy Kirishima or be Kirishma's femboy slut

Kachan wanting to become a super futa like Miss Robbin who becomes his new idol and be the ultimate bitch breaker

What I'm thinking so far is when Kachan and Miss Robin have their first session, its basically her just sniping at him and deliberately provoking him a little because she see's everything wrong with hero society in how this kid cares more about winning than actually saving people, but as the secession continues she starts to pick up his genuine desire to be a hero and starts getting curious why.

And as she pokes and prods him a couple times more she realizes he doesn't know why. He doesn't care about the money, the fame, the girls. or even if people like him. He just wants to be like All Might and be top of the world. Basically like you said her realizing how empty his goal seems to be despite how hard he's willing to sacrifice and work to get it.

And her starting to feel sorry for this aimless desire. An idol that doesn't reflect him us his guiding light. Her wanting to find a path he's invested in for his own beliefs she shaped

It will be interesting to see the path the readers choose for him.

What you thinking for his two or three routes?

His routes all revolve around Deku and how him becoming a great hero really challenges Kachan in a way he hasn't before. But the three big one's I'm thinking is either becoming a villain, basically him acknowledging Deku's the hero not him. Him becoming a hero, but a darker one that can let Deku be the spotlight, the true hero to guide, and him as the one in the dark that handles the dirty work.

While the last route is called surrender, because its Kacchan acknowledging Deku's the true hero but instead of rejecting it or working behind it, this Route has him trying to become like Deku and raise himself into a true hero as well.

How does the smut and body mods vary?

Not a hundred percent sure yet, I'm thinking of having that one quirkless scientist working for All for One, introduce a drug that amplifies quirks but also their side effects kind of like a steroid and Robin will have the ability to give it to various students and make them stronger with various side effects. Stuff like frog girls tongue gaining the ability to stretch, or Momo's breast going full hyper mode