Let me set the record straight: Evelynn was the evil seductress long before Elise even existed. Seeing as this is a rework and not a new champion it would be incorrect to rework Evelynn into anything other than what she already was.
Second, Elise is not an evil seductress. She lures people to offer to the Spider God, but she doesn't use her looks or charms, rather she gets them to willingly come through their dedication to the Black Rose (in the old lore, I think she had a cult, which I think is cooler, but the statement still stands, she does NOT seduce people sexually).
Third, while I think League is over saturated with femme fatales, very few of them openly use sexuality, and the ones that do are all very different. I already mentioned Elise and how she near worships and serves a Spider God. MF seduces men, but it's usually a means to an end, she's more interested in her political goals; she's not actually a flirt, she actually seems rather serious in her recent lore, but she's not going to waste a good resource(how she would see it) like her sex appeal. Evelynn is the closest to a traditional "seductress" trope. And Ahri has a morality issue: she seduces men and sucks up their life essence to become human, but the more human she becomes, the more she feels bad about it, making her much less evil than initially thought. Of the 4 ladies I mentioned, only really two of them are considered truly evil, and one of those two has a somewhat sympathetic backstory, the other I don't think is human. I would consider all of them powerful in their own way.
Sexuality is actually not explored that much in League of Legends. There are a bunch of female Champions that could easily fall under "femme fatale" but for most of them, sexuality is basically non-existent. Katarina looks hot but does NOT use sexuality, only her skill with knives and her primary motivation revolves around her father and her family in general. Fiora is hot, but actively refuses to marry and duels everyone she can to prove her power, again only caring about the family status. Vayne is attractive, but she studied dark creatures and how to put an end to them, becoming a vigilante, all motivated by her parents' deaths. Zyra is a plant that has taken a human form for survival, not even technically a woman. These and more are women in the game that are very voluptuous and good-looking but sexuality plays zero role in their lives. This may just have been Riot's early design patterns, where most women were pretty conventionally attractive no matter their background, but there are Champs like Lissandra, Jinx, Illaoi, arguably Irelia and Lux, none of which are strictly conventionally attractive, so I think the variety in appearance is increasing and that's good.
Discussions like this are fine to have, but honestly female champs in League are becoming less of an issue. They're getting better about providing face and body variety and for the most part aren't giving in to iffy tropes like the "femme fatale" or any other variety of sexualizing or damseling. The women in League have always been powerful in their own right, and less emphasis is being put on their appearance. Tropes are tools not rules, and I think Riot is getting that with this new Evelynn re-imagining. It's ok to make a character based around an archetype, it's not ok to make a character who is nothing BUT an archetype, and Riot is doing a good job avoiding those pitfalls as far as female Champs are concerned.
As I finish writing this, I realized we JUST got Xayah not that long ago, probably the most sexually open Champ since ole Evelynn herself. If you play her by herself, she's not very sexual, she's only sexually open with her partner, Rakan, which makes perfect sense. And while I don't personally like Xayah as a character (not that she's a bad character, just that I disagree with her mentality as a person) her relationship with Rakan is something I think we can all admire, and Riot presents it as something desirable. If that's not a solid example of "good female sexuality" I don't know what is.
Heck, even Illaoi is open about how she had a fling with Gangplank. I don't think there's anything on Runeterra that could shame that woman.
