Concerning skill-unlocks… I’d like to see this in addition to a resource based unlock:
I really like that nemesis-idea that someone mentioned earlier. So building on that, I present you one of my favourite game-experiences so far:
The doppleganger.
The doppleganger is the same profession as you are, and the same race. It is a shapeshifter that has only one purpose: to beat you in combat. It gains a small stat increase every time that it is defeated. (Up until a certain maximum)
Background story: After an epic battle, you have managed to lock the doppleganger in an instance. A prison from which it cannot escape unless it defeats you. So that is what it will try to do, whenever you enter the arena, it will fight you. And learn… yet after a while, it figures out that simply copying all that you can do is never enough. So it meditates, thinks, and spends days/weeks/months to practise it’s moves. Time is irrelevant in the arena, centuries in the arena are like minutes in the open world.
All this, to be ready whenever you arrive.
The arena
The arena is like augury rock, a mystical zone, locked away from the rest of the world. (There is a PvE and a PvP version of this arena) And it has five locks to prevent the doppleganger from leaving. You can fight it on your own, or in a team of two, in which case it will scale up, but use skills based on the instance owner.
Everytime it defeats you, it will feast on your energy and use that to open a lock. After it has opened all five locks, it will escape and you will have to chase it down in the open world.
The chase
Whenever the doppleganger is loose, it will leave a trail of destruction in the open world only visible to you and your party’s eyes. Like the blackest of cracks through the earth. Or purple ones through the mists.
Of course you don’t have to track it down on your own, the priory, vigil and order all have their own ways to locate this monster. (Chasing it down should never take more than 10 minutes)
And it may just start attacking you at any time, surprising you and your party.
With a capture-skill that you can get from the arena-keeper, you can beam it back to the arena. After that it will be easier to defeat than at the previous attempt.
The unlock
Everytime you beat the doppleganger, it will teach you a skill for your profession that you don’t have yet. If you already have all the skills for that profession unlocked. It will just reward you a skillpoint and a champion lootbag once a day or week. (It could also pop up on the daily achievements list)
Extra’s
How about a dps calculator, like the master of damage had in GW1?