Blizzard keeps thinking of ways to incentivize PvP for the casual player to fix the diminishing player pool. Why not reward the hardcore, top-end players instead? Why not fix the ladders, purge the exploiters, and provide the top 0.5% of Arena and RBG players with even better gear?
Because if they purged the exploiters and the scum, a lot of the top half percent and people that are actually good at the game would be pushed out with that purge. That's just the sad truth, now more than ever the people getting R1 and Glad are doing some really scumbag shit to get it because it isn't as accessible as it used to be. I don't think that will ever change. People know they can DDOS, wintrade, and exploit to get their rewards, so why bother doing it legit?
There's no reason somebody in the top half percent should have any actual gear advantage over the average player. Giving those top people better gear will only make people more likely to scum their way to the top.
If it was easier to get the best achievements/vanity/etc then people might not be so inclined to scum for them, but it will make them less special. There really isn't an easy fix, but lowering the barrier to entry for PvP isn't a bad thing.
All that said, I think prestige and vanity gear/mounts/flavor items should definitely be introduced for 2200+ arena. RBGs already give some cool stuff like titles, mounts, and oldschool transmog gear, I feel like Arena should be more liberal about handing these things out in order to get more people participating.