Well, to make it economically balanced, you need to make EVERYTHING untradeable. Otherwise, a huge number of afk-people in dredgion are just waiting for us. And yes. AP is very easy to farm. Incredibly easy. Especially if you already end-game-geared.
We can talk for a long time - why this will break the balance of the game to hell. One of the reasons this server live for so long is the lack of such "improvements" that break the original concept of the game.
How about just playing the game and have some fun?
Of course, it will be nice to gear up the character, and abuse pvp activities for him, displaying up and medals as kinahs, and then selling the kinahs for real money (otherwise, the point in this whole idea with the exchange simply disappears, for what, when the character already has a end-game gear?). Well, or, as an option, to further widen the gap between new players and those who have been playing on the server for a long time. It's probably cool to kill newbies with two skills. (sarcasm)
In any case, the idea itself is not a bad one. But not viable, given the specifics of Aion. Otherwise, the Koreans themselves would have introduced such a function in this version of the game.
In the realities of a pvp server, this concept could still be possible. But not on classic pve.