I started writing a really long reply about how this idea should not be implemented. Then I decided to save myself some time. Everyone is just trying to 1up each other anyway at this point.

The Taru, Duuude, is correct. A system like this seems like it might work on paper, but it's more like an excuse to reduce the responsibility of actually fixing an issue.

Reasons people RMT:
Time investment too large:
Derives from requirement of monetary gains through large amount of dailies, crafting, etc.

Price of entry too high:
If the game does not pace income appropriately the need for quick gain rises. If I'm leveling up and hit the highest level, but everything costs x57 what I have, well then sir (or mam), we have a problem.

Consistency of game rewards lacks:
If you constantly complete content and are not moderately rewarded. How about those endless runs for Darklight gear? I'm not saying they should be easy to get, but COME ON. Also, remember Diablo 3 at launch? I forgot that game was supposed to be about loot until they reminded me on a forum.

Furthermore, if I'm constantly receiving really good gear from completing crafting milestones, quests, or instances, why would I need to purchase in-game currency?

Staying competitive:
There are no systems in place to catch newcomers or casuals up to current content. Why do tier 1 content when the tier 3 patch is out? "Wait, I haven't done tier 1 or 2, so how can I do tier 3? .... Guys?..."

Your game isn't fun:
Read the title. People want to beat it fast and experience what it has to offer. They also want to get out quickly.

In conclusion, fix your game. Don't implement a lame feature for extra income because no one wants to actually pay a subscription. This is a pointless system for users - why do we need it when everything we want is obtainable through moderate play? I actually think this game may already be trying to address this issue with its crafting, gathering, and battle systems. Each can generate items that are good for selling or using. Don't have time to run raids? Go weave yourself a new shirt, brotatoe.

Be careful though and don't make the game one linear tier of content and rewards. World of Warcraft has done a superb job implementing rewards for all play styles. You want the best loot? Well go wipe on bosses and rerun content over and over until your guild breaks up for that highest bracket gear. Want a similar piece of gear, but with less stats? Well go run into a wall while your party kills the boss for you. Either way the different play styles are rewarded.

Using the "But Mom, it worked for EVE and her friend TERA down the street!" mentality - Why not do something a bit more interesting, more Final Fantasy? Why not implement a system like the digital store in Guild Wars 2 (minus the boosting items)? Maybe do it via the Gold Saucer. Spend Gil or real money (which has a controlled and moderated conversion rate) on tokens to play mini-games for character cosmetics or a new rug for your house. Now the developers have more money and I have a badass Mithra rug.

If you're more worried about revenue stream for the developer, well then, the above would suit them better. Knock out a mount skin asset in the afternoon and sell it for $25 starting Friday. Little work for an unforeseeable income over the game's lifetime. Not only that, but the cosmetic addition to the game's store introduces zero balance issues.

Unless, of course, it's unfair to be a badass.