That is a interesting postulate :
And let me add this postulate:
… and a de facto and de jure independent unit by default…for all practical means that matter (as long as it keeps things “ugly 4 compliant” ).
The reasons why nobody is likley to attack it with missiles are the same why nobody will attack a cruise ship with missiles…it is not something serious people would be concerned about, or talk about…or consider in any way…or see a need to plan for in any way in a serious business plan.
… and it matters very little in practice if the shore distance is 1 mile or 200 miles … the independence status of a floating entity does not depend on “shore distance”.
Nobody tosses the beer over board because the cruise ship is cruising in sight of a coast that has sharia law in its courts… and no armed patrol boat will come out 199 miles to “enforce sharia law on the international cruise ships passing by” that is not the marine business practice…
That simple fact of internatioal marine interaction should be obvious to everybody - the ocean is not a patchwork of legislations and hostile nationalistic enforcements imposed to anybody floating out there (according to zoning). Who postulates this and on what base ?
There is only ONE emergent law that matters “freedom of the ocean” for everybody (as smallest common denominator everybody with economic power can agree to).
No enforcement of national rule sets of any kind for nobody outside of harbors and marinas. That is what works in practice - the rest is "pretentions", "dead lawtext", and weak UN conventions some agree to some not - (who gives a ship about them - for all practical means...)
Postulate: The shore distance you need does not depend on "articles and legal papermousing in UN conventions and dusty 17th century admirality laws" - it depends on how much of a "hostile oceanic bulley" in practice your neighbour is.
In many caribbean countries you will be good with a few hundred meter shore distance to enjoy interference freedom of 9.9 on the interference freedom scale.
Caribbean Nations are born along the liberty ideals of Simon Bolivar. Independence is welcome, normal, and universal, the "out of jurisdiction status" is not seen as a "threat to the founded and grounded national(ist) state" but as a default in the natural come together of multicultural societies of multiple makes, traditions, sizes, ethnics, and world views ...
Nobody in the Caribbean will even waste a thought on "how big government conform" according to which rule set, something that floats over the horizon and out of sight - clear subject to the freedom of the seas - in the end - is - or should be - or is supposed to be ...or which grade of independence it declares to whom at what point of its development...
My educated guess: It will go like cruise ships - they live their life as de facto independent units in all aspects that matter - without declaring anything to anybody - at any shore distance - and any zone - legally they are “in the same class as a canoe” - but their practice of interaction with ports nations, supply lines and international networks is VERY different it is almost a form of economics diplomacy with very strong cards to play. They get the best of many statuses - and leave “unconsented interference” behind - ALLWAYS and at any level…they have no interest in being treated as a city or a state because their actual status is much better … it is about business, interference freedom, global markets, and global networks, not about politics. It is more about “getting rid of politics in all its forms” as Peter Thiel puts it.