The token idea would require massive amounts of coding, would massively hurt revenue for the game (and make it shut down cause it's not making money anymore, it's too easy to make gil for established players) and would be abused by RMT.
Well yes and no. The concept of a sub token is you can buy months of game time in the form of an in-game item, which can then be traded/sold in-game to other people. The idea is that whales (people with lots of money to burn) can use them to get gil or trade for stuff in a form of "sanctioned RMT," while people who may be short on IRL cash but have lots of gil can spend the gil they earn on these tokens to play the game for free. It's supposed to give the game publisher a piece of the RMT pie while reducing bots because the real players become the "bots." But in the end, the RMT just play the system too and it really just doesn't solve anything.