Leona's decision tree and her E
This will end up being a buff to Leona. Just keep in mind it's not a buff for the sake of power, but for the sake of giving her more options in different situations.
Problem: Right now Leona has basically 2 choices in any situation: do nothing or go all in.
Give her the ability to reactivate her E to move her back to the original cast position. The window in which she's allowed to reactive the ability should be tiny - just long enough for her to Q and get out. This allows her to make more of a decision. She still has to be aggressive and engage in order to do anything, but it doesn't always have to be an all in.
The reason the window should be tiny is so that she can't get a full combo off. If she wants to get the W damage out then she'll need to use it well before she Es, in which case your opponent should be able to see it coming and back off at the right time.
I know Leona's a very viable pick, but her decision tree is practically non-existent. This just gives her a little more choice.