There are only 2 ways to stop rmt, preventing them, fixing some exploits etc are good methods but not enough, a lot of rmt prevention outside of preventing botting (will require a lot of time, and could well end up futile) and fixing exploits are good ways to go, but outside of these methods it will start to impact legitimate players. a small FFXI example of this was placing Goblin Bounty Hunters on party camps which at the lower range of the party could not be defeated.

The other way is for players to stop buying gil, once demand lowers they will realise that there is no point in trading in FFXIV, and would therefore vanish. The latter is the easiest and most cost effective way, but people won't stop buying most probably out of laziness.

Any account based restrictions can be easily overcome by rmt by making a new account. They add a level limitation to /tells bot some FATEs, add a quest for them, they could set up a bot to do the quest, all they need is the NPCs and map coordinates and which mobs they might need to kill, and which (if any) items the bot looks out for. Any IP or Mac address restrictions can be overcome in seconds by changing, or spoofing said addresses.