I like to use fictional ship names for Command. First, using fictional names lessens the need for the sort of direct 100% accuracy, such as putting a ship in the wrong geographical area. Second, I simply like thinking of names.
For navies/ship types with established naming conventions, (people for American destroyers and frigates), finding a name is easy. This applies not just to types but to individual classes. If a certain class of Soviet destroyers was named after animals, I can easily pick out fictional names.
There are two stumbling blocks for ship names. The first is if the units are rare and valuable enough that one has to use them. For France’s carrier, unless you have an alternate history where they built more, to use any name but the Charles De Gaulle is inherently inaccurate. Even though there are considerably more American carriers, each one is distinctive enough that it feels off to name one differently.
The second is units that don’t have names at all, but just numerical designations. When it comes to substituting units, it’s easier to swap “USS Morgan” for “USS Fletcher” than it is to swap “U-100” for “U-99”-both existed, while the Fletcher-class “USS Morgan” did not. Either I would accept some inaccuracies or find what number the sequence stopped at and name the units above them.
Of course, for ships never built at all, one can be extra-creative with the names. I had fun naming a Project 71 carrier (historically just a paper ship) the Marshal Tukhachevsky (after an innovator in combined arms warfare that Stalin purged). The idea was that Stalin ordered the carriers built, and by the time Khrushchev replaced him, they were either complete or too built to practically cancel. So, as a form of trolling/irreverence, Khrushchev would name the carriers after Stalin’s enemies, and one such carrier sailed into battle against American submarines in a scenario.
One can always fall back on the historical names if coming up with fictional ones is too much work, or if they desire greater accuracy. But there is something to naming one’s own fleet.