It might be more economical to farm out the incarceration of violent Palestinian detainees to other nations at a lower price. Cost of detention centres in El Salvador offers economical rates, and perhaps some sub saharan nations would have options open. Of course, the floating islands should be reserved for the displaced, until they can get their feet back on the ground. But the floating islands, without proper navigation and anchoring systems, risk that the Mediterranean winds and currents take the island through the Pillars of Hercules, out into the dangerous strong waves of the Atlantic.