I would love a Plex-like system. Games I've seen this work marvelously in include the aforementioned Eve, TERA, Rift, WildStar, WoW, Guild Wars 2, ArcheAge... probably more that I don't know about. Rift, GW2, and WoW also let you take your gold and convert it into cash shop currency, which means not only can you pay for your subscription if you want, you can buy other things off the shop as well.

It doesn't really hurt the economy at all.