Change the status you now get from pvp kills to a new status called "pvp status" calculate this new currecy for being able to buy new pvp gear. then maybe add another for BG gear and require both tokens from writs/bg wins and the new status for each type (dont share them), and remove the heirloom tag ffrom the gear.
This promotes both things open pvp and new BG's while not rendering previous tokens worthless or instant purchaces on new gear or giving pvp players an advantage by keeping the paths apart.