I feel like Masteries could be a lot better if there was a way to get other Keystones.

Much like the rune page system, I would think it would be amazing if you could acquire other keystones instead of the nine we currently have, because in most cases. The best one to pick is just kinda meh, for certain champions. An only champions that can make 100% use of the keystone will always have a better advantage.

Why not have it so each Mastery page is like a Rune page. You pick Five Lesser "Stones" Each one a barrier to a Greater stone for, four Greater "stones" and your one "Keystone". Then have five keystones for every roll. Five keystones for Junglers that would specifically help a jungle clear faster, gank more efficiently, gain more health and tank stats, get stronger for stealing the enemies jungle.

Then have Keystones for the Tanks [More sustain in lane, a way help last hit minions, reduce damage by a small fraction, dealing pulsing damage related to your Armor and MR. Maybe a Anti-Seige keystone, where when around a ally tower, you slowly gain a shield, that also increases the shots of towers every third hit or something.]

Brusiers, [Grasp of the Undying is fine, but stuff like, building AD or AP gives you abit of armor or magic resist. Maybe a cc-resist when chasing targets, or something to really show that they are Juggernauts, like attacks reduced the movement speed of targets every now an then.]

Just in general, things that could allow champions to play rolls they normally can't. Why not make Yasuo, Mordekaiser an Jayce a viable ADC botlane? Or Annie, Kassadin, an Malzahar a viable jungler? Or have other things become, "Hey that could work with this Keystone because it gives me what I need to be viable and do my job as that roll." Of course meta would weed out what's viable if this may ever happen. But the possibilities of team comps and keystones that truly, "Change the way you play a champion" is here yet. Because right now, everyone sticks to one keystone for a champion. Not several "Hey this is my keystone for my AD Yasuo Mid, the keystone for my Yasuo ADC an my Bruisier Yasuo top." Each with a different keystone, and lesser stones that allows the viability of the champion because it gives that champion the tools necessary to be viable.

Because, people I would imagine love options. Or love to play stuff off-meta, because it boring seeing the seem stuff, over and over an over again. Same champions in every game, with no variants.