I mean, a better gil sink would just be for the players who feel they have too much gil to just throw the gil away. Find the NPC vendor with the most expensive stuff you can buy for gil, spend all of your "too much gil" there and then vendor the bought items back for vendor price. Boom. Gil gone in a way that doesn't impact the economy. As a bonus, the devs don't need to spend any extra time and resources creating stuff or new systems to stroke anyone's large.. wallet.