Where you can exchange your PvP Faction points for crafting materials, dyes, Ectoplasms and other such PvE niceties? Granted, they'll probably have to raise the faction cap for this.
Maybe something like:
15,000+ faction - 1 Glob of Ectoplasm
5,000 faction - 1 Obsidian Shard
10,000 faction - 1 Black Dye
250 faction - 10 Bolts of Cloth
(Conversion rate will be based on Trader rates)
(Maybe add in another condition where you can only do this conversion when you've unlocked everything else? Or not?)
And so on. It'll also help to connect PvE and PvP together and for those who have already hit the faction cap (10k) and have had everything else unlocked, it'll give them something to do.
Now before you guys go: "OMG! Then people will just Faction Farm!! WTF?!". Well, like I said, it'll help connect PvE and PvP together.
- PvE's already full of farmers. Now you can farm in either, in whatever style you prefer.

"OMG!! Then skilled PvP guilds will have a monopoly on Ectos and Shards!!"
- Meh, hardcore PvE (farming) guilds have more wealth than others too. But other PvE players can get gold as well. Same idea.