Every island out there is already controlled by a government, uninhabited or not - they will not allow you to just take over and build your own jurisdiction. You will still be subject to all the laws of the governing country, so cannot make your own laws. I think Sealand have gotten the closest to this idea, an offshore rig that offers hosting and other online services, along with "citizenship". If their closest neighbour wanted to take them over it could be done with ease.
As I know in "Isle of a man" has not very tough laws too. Because many casinos and poker rooms having the company address on this island.