Mastery
The mastery system really needs a revamp. I have an idea that I think would be extremely beneficial to summoners. You should create at least 2 if not 3 separate mastery builds. For example you could spec build 1 as suicides, build 2 for maybe Mystic dispersion and other stuff. Then on each champion, create a little check button in their bio where you could assign them either build 1, 2, or 3 for their mastery setup. This would allow summoners to run suicides on the champs that benefit from it and also assign a different spec for the champs that are hurt by suicides.