Bit critical, bit rude, but I get the question.
Kind of, a friend of mine which is a writer offered to help teach me to write even better, and help spellcheck the results.
Well, the concept of transformation and mind control are two of my favorite fetishes, so I have a weakness for this type of game.
A few things I noticed:
1) The first transformations for each character should be much less obvious.
Heroines like Raven have a large amount of magical power, and if they noticed that something was obviously wrong with them, it wouldn't be a problem for them to fix it. So the first changes should be small and should teach the character to like these changes so that they are not afraid of bigger changes.
2) It should also be noted that a large number of young heroines work in a team.
So even assuming that they wouldn't notice that something is wrong with them, others would notice and do something about it. So (referring to point one) you'll have to explain why it's not suspicious to anyone else.
"Study holidays" ,
"Vacation",
"I want to spend some time with my parents",
"Sick leave", etc.
3) I like the concept that Beast boy has to somehow get his DNA into other people's bodies in order to change them.
But filling balloons with your sperm and throwing them at people... that's something a 13-year-old adolescent boy would come up with (personally i would remove it completely). Plus, one hot shower is enough to make it all go away. Dirt and various liquids from the surface of our body are not exactly absorbed inside.
4) You should focus on things like:
Cum in food, Cum in drink, French kissing, Cumming inside mouth and Cumming inside pussy.
In the case of heroines, it should be about gradual seduction, possible dating and secret corruption.
In the case of Villainess, you should be more direct, as you don't have to worry about being exposed by authorities or heroes of good. Here you could apply real combat. Beast Boy would have to train his fighting skills if he wanted to survive a confrontation with the stronger villainess. You could fight them, defeat them, and then rape them. They would gradually change more and more and give you less and less resistance or, on the contrary, they would put up even more resistance, because they would know what awaits them if they lose. That sounds a lot better then throwing cum balloons at them.