Couldn't you accomplish the same goal with a lot less hassle and expense by parking a suitably sized naval vessel offshore and designating it an "embassy"? Of course that would be completely inconsistent with the purpose and function of an embassy, but so would a fortress in the desert.

One of the great advantages of proposing things that you know will never be tried is that you will never be proven wrong, and can carry on for all time claiming that your way would have been better. This is not an uncommon device on these forums, though this is perhaps an unusually extravagant example. Those who would prefer to consider the real world would be well advised to follow Jon's excellent example and become elsewhere, which I think I will do.