The arrangement it makes with adjacent governments is nowhere near as important as the arrangements it makes in regard to physical security at sea.

Sealand is a stone's throw from the UK mainland, and even though it is not technically British it benefits from the UK's very well protected shipping lanes and coastlines. Other parts of the world, not so much. For example, they can park this thing off the east coast of Africa and have zero interference from local governments -- for the day and a half it lasts before getting stripped bare by pirates.

A government that won't interfere is likely also a government that will not protect them. They need to choose their location wisely.