I know many of you are asking me via Twitter about the ISS prefix -- I just spoke to Starfleet Command and they let me know that when the Federation needed to make their "minimal modifications" to the mirror ships, they changed the prefix to USS so it could be re-registered. I'm being told that the KDF needed to do the same and updated the registry to IKS.
There are also technical reasons behind it.
Brandon "BranFlakes" Felczer | Former Community Team Lead for Perfect World Entertainment
It actually makes sense, come to think of it, that the ships would have the U.S.S. prefix, like it or not. Why, there are plenty of real-world examples of similar situations: the German heavy cruiser Prinz Eugen, which accompanied the battleship Bismarck on her famous attempt to break out into the Atlantic, survived WWII and was taken by the U.S. Navy, which labeled it the "U.S.S. Prinz Eugen" before disposing of the vessel in nuclear weapons tests. (I guess it was a more dramatic ending for that fine ship than the scrapyard...)
" NX was a registry prefix first used by the United Earth Starfleet for their NX-class starships in the mid-22nd century. (ENT: "Broken Bow", "Fortunate Son"). After the founding of the United Federation of Planets in 2161, this prefix was used for experimental and prototype starship designs. (Star Trek III: The Search for Spock) In the Mirror Universe, this prefix was used by the Terran Empire for their NX-class starships. (ENT: "In a Mirror, Darkly") Two centuries later, this prefix was used by the Terran Resistance Forces for their Defiant-class starship. (DS9: "Shattered Mirror") Ships that use the NCC and the NX prefix are listed in the Starfleet Registry. (TOS: "The Ultimate Computer") "
Know your Trek boi!!!!
Kidding, but that is a good point. we can have the NX, but not the ISS. my guess is some where along the chain of command at the gods who control what we can and can't have have said no. we are star fleet.. not the Empire. these are the same people who say no to the T5 connie..
of course I am just taking a guess. It could be that cryptic wants to put it in the Cstore.