Get ready for a wall of text, this one was a doosey to write. SKIP TO THE BOTTOM FOR A TL;DR AND REALLY THE MAIN POINT OF AL THIS
First of all, lets address the words you put in my mouth. I was not trying to set some bar with my Captain Fortune example, I was pointing out that the iconic sexy League of Legends champion's latest skin is among many other recent skins and champions that are covered up, no matter how low her top apparently is (oooh, cleavage, how horrifiying!).
When it comes to the Pool Party skins, where did I even mention Leona? When did I say she must be in a bikini? I think she looks great in her outfit, I'dve expected her to wear a sun hat (heh) but I suppose that's what the parasol is for. I don't expect Lulu or Rek'Sai (who you seem to have forgotten when you say Leona is the only adult female) to wear bikinis, that'd just look silly. My point there is the Pool Party line of skins is exactly where you'd expect a two-piece bikini Miss Fortune or something, and yet there are no such skins. There are no beach volleyball Ahris or sun-bathing Katarinas. Despite Riot's supposed tendency toward sexual skins, the most obvious skin line for it lacks such a skin completely after two sets of them have been released. Anyone who thinks "League goes overboard with their female skins" clearly hasn't been playing for several years. Side note: Draven does in fact wear a speedo for his Pool Party skin, something you clearly only looked at once. The life vest is just because it's funny.
Now, you say I missed your point but it seems you're really the one dodging mine, so let me rephrase: Who the hell cares what skins they give her? She's the most powerful angel of a race dedicated to destroying evil wherever it lurks. Pretty generic if you ask me, but awesome nonetheless. So here's the real clincher, if she's made to look like a succubus, not actually made into one, what does that change about her? It changes her looks. Does it somehow change her lore? No. Does it somehow make her less powerful? No. Does it somehow make her worth less? Absolutely not. You say her ambiguous design makes her special, but does it really? Maybe in the early years when being an armored up female was a unique trait, but even then you had Poppy. Times have changed, and all it really does now, much like before, is make people who don't know better think she's a man because that's what the majority of people default to when refering to anything. This somehow makes her better than she already is? It's empowering to have people just assume you're a man? The fact that she's one of the most powerful beings in the lore isn't enough, she has to be covered head to toe in armor for all that to be valid? What is the purpose of denying Kayle her womanhood? Is it really empowering to women to repress the fact that they are women? That is truly absurd. You are not doing anything for any group you belong to if nobody knows you're part of that group.
On a related note, what exactly is wrong with sexuality? What exactly is wrong with making sexual and sexy characters? Sexy characters are inherently more pleasing to look at than ugly characters. That's a fact. Why not make characters that are both attractive and have interesting lore? That's not to say ugly characters are worse than attractive characters, being ugly can itself be an interesting trait. That's beside the point though (though I'm sure it's a statement that will be used against me). You can have characters that are cool and interesting and powerful without stressing their sex and still make them sexy or attractive. What makes a good character good in the end is their personality and story, things that looking good don't detract from. So why exactly is it so important what a character looks like? Why can't they be strong and attractive? Why does making something look sexy suddenly make them worth less as a character as you imply? Giving Kayle an entirely optional visual imagining doesn't take away her ult which bestows invulnerability, or her power to shred through even the bulkiest of opponents like paper, or her powerful heal that also boosts speed. You know, the things that actually define her as a character and champion in the League of Legends. Making her look like a succubus doesn't make her less powerful, it only makes her look like an actual woman (as opposed to a suit of armor). If anything, it's more empowering to make her a woman confident in her sexuality, repressing it does the opposite.
Now let's take a look at the 'diversity' issue. The Oxford Dictionary defines the word 'diverse' as such: "Showing a great deal of variety; very different." Much different that how you interpret it, in which you seem to imply my definition of 'diversity' is some sort of oppression. In any case, by definition, sexy female champs and skins are indeed 'diversity' at this point. Especially when a champion who normally is not expressed sexually is given a sexy/sexual skin. The only way you can get more different is to make them a man, or another creature entirely (neither of which really make sense, though genderswap skins would be pretty cool)
When it comes to champions, sexy is definitely something we don't really see anymore. In the last three years (2013, 2014, and 2015 thus far), three of the 18 champions released are what most might consider sexy by usual standards.
Lissandra (very subjective)
Yasuo
Braum
Two males and a single female, and Liss is a real stretch. As far as the other females go: Lamb is a sheep, Rek'Sai is so inhuman you can't even tell she's a female without being told she's a female, Kalista is a spooky emaciated ghost, Jinx is a spooky emaciated ghost, and Quinn is completely covered up. Three years and 18 champions and only one female that's particularly attractice (though I personally think Quinn is pretty cute). You mean to tell me that one or two female champions that are attractive in the last three years (they're even covered up!) somehow makes skimpy and sexy a majority?
And your cherry picking, it needs a bit of work dude. Of 38 (I think, might've miscounted), and of them you've listed 15. Of those 15, several of them are more than appropriately dressed in their base skins, and even when it comes to skins they have one or two each at most that are actually designed to be explicitly sexual. Of the champions you listed, I'll give you Ahri, Elise, Evelynn, Katarina, LeBlanc, Miss Fortune, and Zyra. They are all indeed sexy for sexy's sake and there's nothing wrong with that. But actually, I'm going take away Zyra because she is a plant inhabiting a human's body. She probably doesn't even care to wear clothes. Really, you're lucky she covers up as much as she does with her leaves.
As far as skins for the other champions listed go, how many skins do they really have that's sexual? Akali has a nurse skin, Diana has ????, Irelia shows cleavage in a skin or two (oh no, not the C word!), Janna's skins actually cover her up compared to her default, Fiora has a Halloween costume, Morgana also shows cleavage (crazy that women have breasts, right?), Riven has a community inspired joke skin, and Sona has her Muse skin I suppose (cleavage strikes again!) All of these champions have several skins, and most of their skins are perfectly 'fine' and non-sexual (as if sexy isn't okay). To reiterate, they each have at most two skins that are especially sexualized. Your cherry picked list is only half effective at proving your already flawed point.
My favorite member of your list is Sona, who's long, beautiful dress is hides everything save for a bit of cleavage (her breasts are quite large, even among the likes of Miss Fortune). What I think is neat about her though, is she doesn't show a lot of skin but is still an attractive woman, not to mention interesting. A mute and a musical prodigy with a magical instrument that can either end or save your life with a single pluck of its strings. Arguably one of the most interesting characters in the game and of her era, and yet she's still attractive. Crazy, right?
Lots of shit I wrote there. Am I still missing the point? In any case, there's one more point I'd like to make.
Things like Brand's ice skin, which is a nod to Dr. Freeze, are not fair comparisons to what you're trying to push on us with Kayle. You're taking away an important principle of a character to satisfy sexual desire.
This is absolutely a fair comparison. Both are characters visually imagined differently. In fact, Brand's ice skin, takes away his defining feature (FIRE) and replaces it with its opposite (ICE). How is that not exactly what you claim we would be doing to Kayle if we gave her a succubus skin?
HERE'S THE TL;DR FOR YOU AND ANYONE ELSE WHO DIDN'T WANT TO READ THIS ENORMOUS WALL OF TEXT
Fallen Kayle is a great idea, a Kayle that's only purpose is to seduce men in their dreams, not so much.
That's not what is happening. Giving her a succubus skin doesn't suddenly make her a succubus, just makes her look like one. Her sexual ambiguousness still exists in her other skins. Skins are entirely optional, so who cares what they look like?