It's not relevant. The moment criminality (in the view of other nations with these kinds of laws) hosts itself there, they'll find themselves hauled in front of the UK courts, and find that their "micro nation" isn't recognised and that the UK both claims jurisdiction over them and is able to enforce it.

Sealand is a structure within Britain's territorial waters (since they were expanded in 1987)... From what legal analysis I've seen, a structure just wouldn't ever be considered as a 'nation' in any sense, and if anything happened there that the UK was really concerned about they would remove the occupants anyway... So unless they had a navy that could go up against the UK's...

They'd need satellite internet anyway to get connectivity that didn't go through the UK so not going to be great latency.

It's isomorphic to a pirate ship. Just put your nation on a pirate ship, it's the same legal situation but more mobile.

Note that pirate means no laws apply to you including the ones that would protect you from things like murder.