I think the whole argument is going down the wrong road, the thing what really matters for subscribers, in my opinion, is what will happen next to the game and in the long run. Therefore the only answer to the question "what would be the right reward for a subscriptions?" is to have a say what is coming next.
It's like holding shares!
Subscribers should be able to vote what content would come next and where they think the funds should go.
Every month a vote between PVE - PVP - RP - Fluff - ETC.
Stop this madness off different rights, give them full excess to everything but with a 2 month delay for F2P and 1 month for PP's. Let the F2P&PP's buy the new content for CC's or they have to wait extra until they can participate in a new warzone or Operation/FP.
Just my 50 cent's!