I think it's a little late for this sort of addition. Taking Plex back to its origin, FF14 won't have the same issues EVE Online does with Plex accounts because we don't have FFA PvP and we don't have the player driven economy that controls gear (ships and fits) that EVE Online has.

Still, what FF14 also lacks is Gil value. You could play this game to end game, flat broke and be fine. You could have 50 billion Gil and not even have savage content unlocked. Once you add a Plex system, you define Gil but for the guy with an extra $15 in his account, why does he need Gil all of a sudden?