I play a game called warframe,
On this game you can buy anything you can farm, as well as skins and cosmetics.
On FFXI they could make it so that you have to buy everything with crysta.
They could sell all farmable items like dynamis coins, alex, snowslit stones etc. This makes money off impatience but a f2p player can still easily farm all these items.
Cosmetics could be like the cosmetic suits that the dev team have already been making, the behemoth outfit, goblin suit and the other cosmetics.
Also xp and gil boosters.
This isn't p2w before someone says it, this is pay for convenience.
This system would turn a marginally profitable game that Square have little interest in into a much more profitable one with a very strong future, many f2p games don't have massive numbers of servers or players. They just give more options to make money.