A proposal: Once everyone's vacated the spawn island, we bomb the place with TNT, and construct in place of the now-vanished island a large compass of sorts, with a house in the middle with a few chests, beds and supplies, and at the edge of the compass are arrows or signs pointing in the direction of warps and listing where they are. Then, we get the whole area protected, making it utterly impossible to build there.
How's that sound?