Obviously, RMT is out of hand. People are buying gil. That isn't going to change. You are never going to eradicate that problem. So, why not embraced RMT?

Why doesn't FF14 go down the same route as WOW, EVE, Runescape, GW2, etc?

Sell subs (or store credit) as a token. This token can then be placed on the market for those that want to buy gil.

If supply of the token is more than the demand, the gil price is lower. If demand is higher than the token supply, the gil price goes up.

As mentioned, this is never going to completely get rid of the gil sellers. However, in WOW, there was evidence that the number of sellers plummeted. This is because many companies had to cut their already razor-thin margins and many couldn't survive. Even now, there are far, far less gold sellers in WOW than there was pre-token.

There will be some players that get to offload their overloaded gil in exchange for a sub.

There will be players who want gil and will buy the token.

Those players with overloaded gil won't try to sell to shady sites (and yes, this does happen. It isn't just bots farming the gil), and nor will the players wanting to buy gil, because with a properly controlled market, the price should be fairly level with gil selling prices.

Right now (I just took a quick Google search) the price of Gold for WOW from a seller is more expensive than buying it through the WOW token. This is based off of one site.

SE benefits because people are buying the token, combatting bots, etc.

And yes, there may always be the odd person that bots for their sub, but meh. They won't exactly need billions of gil.