The GTS should stay. Even in its current form, it is still better than nothing ;-).
However, Gamefreak really needs to fix it. As others have stated before, the amount of trolls/hackers requesting for underlevelled legendaries and evos I see on there is beyond ridiculous. I search for a Sableye that is obtainable ingame (in hopes of getting a DW one because I don't want to even touch the dream world, Prankster is awsome) to find inane numbers of these trolls requesting for level 1 or 100 legendaries just for a Sableye. As it stands, the GTS is pretty much how I would imagine 4chan to be like in terms of the number and ferocity of trolls on there. However, more than minimum level limits are needed to eliminate these trolls because with only that in place, the trolls that were spamming underlevelled pokemon will only begin spamming requests for level 100s, which I have no solutions to yet.