Keystone Mastery Ideas for Vision
Since Riot's mentioned they want more keystones, why not make one that centers around improving your ability to contribute vision for your team? Supports (and some junglers) would like that, I'm sure. Here are some ideas:
Sentinel's Vigilance: Your ward cap increases by 1. Gain a small amount of armor and magic resist, scaling with your level, for each green and/or pink ward you have active. The resistances do not apply until six seconds after placing a ward, and last until they expire or are destroyed.
Banisher of Shadows: When you place a ward, for a few seconds it provides greatly increased vision range and highlights hidden enemies, as well as granting you a shield for a few seconds (on a long cooldown).
Scouting Sprite: Your champion is followed by a small glowing orb that has the same sight radius as you, and trails behind you at around a 2-second delay. If you use the last charge in your Sightstone, it disappears and replenishes one charge, reappearing once you recall. If you die while it's active, it transforms into a blue ward.
Swiftrunner's Guidance: (inspiration credit to vSynthesize) Wards you place last 15% longer, and generate a buff over a period of time (scales down with level, somewhere around 30-10 seconds) that surrounds them with a windy circle. When an ally walks into the circle, the buff is consumed, imbuing them with a burst of movement speed. This wind is faintly visible to enemies.
Prophet of Retribution: (inspiration credit to The Djinn) Your wards are protected by a shield that absorbs the damage from one attack. This shield recharges after 20-5s (scales down with level). An enemy that breaks this shield suffers an 80% slow that decays over 3 seconds, and is revealed for that duration.
I know these are pretty niche, but I think broadening the options of keystone masteries to include vision effects are a great way to make the support role more dynamic and fun. Feel free to give feedback on these ideas and contribute your own!