My thoughts on the future Kayle rework.
If we think of what makes Kayle, well Kayle, 2 things come to mind : her ult, and her E. For her to keep her identity, those 2 things should remain, in one way or another.
First, her ult. I think this is the one part of her kit that should stay the exact same. It's a good ability with a lot of uses, and it is pretty unique.
Second thing, her E. The E is pretty boring for an ability, has it is almost just something you have to remember to activate. So, it should be her passive instead. "But wait, isn't that ridiculous?" Well, it's almost always up anyways, and she would lose her resistance shred passive, which just feels like free stats. If it ends up being too strong, it could have X number of attacks before going on cooldown, scaling with attack speed and level.
Being an hybrid champion, it is hard to build penetration. So, with her resistance shred passive gone, she should still have a way to shred armor, but it should have more counterplay. And that's where the idea for her new Q came from.
Her Q should be a skillshot that comes from above (see Xerath W), that would look like a smite from the heavens, which would totally fit with her angel feel too. It should have some form of resistance shred (numbers and scaling up for discussion). Maybe it should also slow, or that could be the job of another ability.
As for the 2 abilities left, I haven't found an idea yet, but they should be more interactive and less point and click than her current ones. She shouldn't have any hard CC as there is already too much of that and it would make her overloaded. Her having a heal or not is debatable, but if she is to have one, it should have some sort of special interaction.