In terms of visuals, animations, sound effects, dialogue(granted Kayle has limited dialogue) and overall thematic they seem very similar. Even their ideologies expressed in their limited dialogue has a lot of crossover. Even their booty tight suits!
I was wondering, is there any chance they are from the same alternate universe?
If so then I really like the choice of costume for this universe's fighters for justice. :^)
Aetherwing seems more technology based
Dawnbringer Riven is (according to the comic) an ancient entity predating the universe itself. Aether Wing Kayle is clearly from a technologically advanced future. Even if they are from the same AU they would not exist at the same time, so the question is somewhat moot. Prehistoric Cho'gath might be in the same AU as the Star Guardians, but their stories are discrete.
But, the Vs comic shows a battlefield covered in the corpses of angels that look remarkably like Kayle. So perhaps the AU of Dawnbringer Riven is in fact Kayle's world from the old lore? In this case old-lore Kayle and Morgana would be fighting the war that Riven and Yasuo left behind. Kayle's lore really has no place in post-retcon Runeterra, so it's fair game for a skin-line without confusing the canon. If so, Aether Wing Kayle would indeed be from this AU, as she represents the utopia created if Kayle wins the war.
I'm no expert on any of these champs, but it seems as though the dawnbringer and duskbringer skins are a better implemented version of the dichotomy between Kayle and Morgana.
In checking out Kayle's skin trivia, apparently Aether Wing is "from an alternate timeline where she lost her wings for unspecified reasons and forged a pair ailerons to replace them.", so I'm not too certain if that'd be the same timeline as Dawnbringer Riven. (http://leagueoflegends.wikia.com/wiki/Kayle/Trivia)
