Whoa, I love the ideas you have going on in here!
I'm the Producer on the Thematic Development Team for PIE (Player Immersion and Expression aka "Personalization") on League, where we source new thematic ideas and develop them through narrative and visual exploration. We're always striving to make cool stuff that y'all love, so posts like this get us so excited and inspired! I really like where you're going with all of these, and I can say that there are elements from a few of these that we've taken inspiration from before.
I personally really love the Battle Mage idea. Reminds me of Guild Wars Elementalists, Battle Mages from Age of Sigmar + Elder Scrolls, and Steiner from FF9.
What kind of aspects do y'all see in some of your favorite skin lines? Or aspects that you'd like to see that haven't been represented yet with our current thematics?