That'd be pretty cool. It'd also go partly to explain why Lily has second thoughts about using her powers on Rin (not sure if that's still a thing or not, going through kinda slow). As Ryoko has the possiblity of being Kei's "girlfriend", would it still work on her at obedience LV4?
Rin, I think, has something else going on with her. She may have some weird lineage that'll play a part in the story later.
As for Ryoko, the glasses do still work with her at obedience LV4, seemingly more so than the other women, given the things she does for Kei. I mean, you can technically go anal with her by LV3 using the "Surprise" and it has no negative repercussions. And she'll readily go ass to mouth at LV4. In her case, it might just be that she's so desperate for love, that the glasses have a stronger suggestive effect on her.
Another example of someone who has resistance, at least currently, is Hanae, who won't let you get that pussy even by LV4. This could be a hint that, despite liking Kei a great deal, she's incapable of being in love, in love with him due to him not being a woman, or it could be a hint that those with a strong will or attachment to a specific moral or ideal, are harder to control, which could coincide with the love theory somewhat, as love would imply a strong attachment to a person. I'm interested in seeing if the girls will have another scene for maxing them out, as that scene could be where you fully convince Hanae to let you have proper sex with her.
Speaking of Hanae, it'll also be interesting to see if Nabila will let you have sex with her, given how in Shizuru's extra scene, it's revealed that Nabila wants to save herself for marriage due to her religious beliefs, which could imply th. If she has a strong moral attachment to her beliefs, I believe she'll be another Hanae, and vaginal sex will not be possible with her as well.