Though I'd want the season 5 runes and masteries back, at this point I'd rather just not have runes or masteries anymore than deal with Riot trying for 3 years to fix what was built broken. Keystones will NEVER be a healthy addition to the game and will ONLY harm balance and champion fairness, and until they figure that out, we'll be stuck in state of perpetually toxic gameplay because balancing both the (awful) reworks or "modernizations" of champions, and the keystones we all abuse in order to compete, is impossible.
Riot, make this easier for yourselves, bite the bullet, accept that the new masteries are an irreparable clusterfuck, and just remove them so you can balance the champions based on their kits rather than what keystones they (ab)use.