It's actually better in every possible way.
1. Players will see drastically less RMT spam in-game.
2. Players will have a much lower chance of having their accounts hacked. Pretty much the entire reason we have two-factor authentication is because RMT companies will do everything they can to hack into player accounts so they can drain them of money. Less RMT demand = less RMT activity = everyone is safer.
3. There will always be RMT. MMO devs with more experience and money than SE have done everything they can to snuff it out and you just...can't...kill it. The only way to beat it is to offer players a safe, legal means of doing it.
4. In the case of the developer doing it, all they're doing is acting as a broker between two players: one player who has an abundance of in-game money and the other who has more RL money to spend.
5. RMT companies tend to also farm up millions of in-game currency that causes inflation. If you ever wondered why the prices on marketboard items are so high, it's very probably due to the presence of RMT companies adding lots of additional currency to the game. Plex doesn't add currency to the game at ALL: it just moves money between one player to the next in exchange for game time.
6. It's better the money goes to the developer where it'll be spent on adding new content to the game instead of to RMT companies where it'll be spent on figuring out better ways to crack SE's security systems so they can hack into player accounts.
Seriously, this system works wonders in so many other MMOs that I'm actually very surprised SE doesn't have it already...
They're not "free". It's just that someone else is paying for their sub. SE still gets the same amount of money either way (possibly more).
When?
WoW tokens hover at around 50,000g as of ~6 months ago. You sure you're thinking of WoW and not some other MMO...?
It's far less of a middle finger when the person who invested the time is being given a month subscription in exchange for this money, instead of it going to an RMT company.
It hasn't "screwed the market" in EVE, WoW, or Wildstar. It wouldn't do so to XIV, either.
-People will get banned/suspended.
-People will stop buying from RMT.
-We won't have to deal with annoying RMT spam every single time we teleport into a major city where they replace the barking bot every 30 minutes with yet another character that we need to report and blacklist.