I don't see why key fragments shouldn't be purchasable with IP. It's not like you can get chests any way but S rank performances in pvp, and even then, you can't get more than four in a month. The whole key fragment thing seems completely pointless. If you COULD win 4 chests per month, but under the new system of honor you are guaranteed 4 keys per month if your behavior is good, then what's the point at all? Why not just let people open chests when they earn them without the extra hassle of key fragments?
Does anyone seriously PAY for keys? Real money just so they can unlock a chest that might contain something they don't even want? Seems like an absolute waste of money to me. I disenchant half the stuff I get from the chests. I'd never pay for chests or keys given the fact that half of the RANDOM stuff in them, I wouldn't even use.