The Syndicate may be an "unnecessary evil" as has been said, but is still the lesser one... there will always be someone to fill their shoes if they are taken out of the picture, and the new ones are always worse than the previous generation. The Syndicate are a legalized government body and even tought they are indeed corrupt, they still needs to operate somewhat inside the law, with the other members and the Sultana keeping each member in check if they go too far like Teledji Adeledji... They also have the best interests of Ul'dah in mind, since a rich Uldah is a rich Syndicate. You remove them from the picture and\or criminalize them and a new criminal organization will replace it instantly, one which won't have any qualm about bleeding completely dry the city without a tought.