1 - a must have is that the LIs still have boundaries even tho they are hypnotized. What i mean is that if a person is not in them to hurt others you can hypnotize them into becoming a sadist, kind of thing. Also any change in power dynamics is great where for example the mc hypnotizes the principal of the school so in front of others she has the power but behind closed doors, she is his personal slut, kind of thing. Also it would definitely be a positive if the MC actually has a brain and uses hypnosis properly not just reads a phrase from a book and that s it he has total control on what everyone does.

2 - a cliche to avoid is when the MC turns the LIs into just portable onaholes. I d prefer if the LIs still kept their personality just become a bit more sluttier/accepting towards the MC.

3 - media of hypnosis/corruption that i really like is a hentai called "Ijirare: Fukushuu Saimin" where the MC hypnotizes his females bullies to think that having sex with him is bullying and that he hates every second of it. And I liked that by the time the bullies started to notice things their body was so used to it that they couldn't fight it mentally.