Would be a shame to screw up something really good with f2p. As soon as one guy that can afford to spend a few hundred per month (whale in dev terms) gets an unfair advantage over the vast majority that can't, the game is major broken and a ton of people would stop playing very quickly.
The thing that makes MMOs work is an in-game economy. Even with illegal Gil sellers a portion of that 'money' trickles back down to someone playing the game.
Sell fantasia
Sell mounts.
Sell furnishings.
Sell minions.
Sell houses.
Who cares, but you start selling armor and weapons, and even buffs like 24 hour exp bonus or something like echo, this game is dead.