Nice lookin' Bengal.
Anyway, if you must take historical usage of naval warship designators into account for usage in example WC registries, then look no further than current day Navy's.
The "X" in for example "CVNX-78"(next generation CVN for the USN), does mean experimental, but so far this is the only new class ship which has ever used this designation.(For example, neither CV(A)N-65(Enterprise), or CV(A)N-68(Nimitz) used this letter designation)
The newer CVNX-78 is given the "X" simply because it's a new approach to carrier doctorine as originating with strategical air wing deployments compared to earlier vessels which were straight on expansions of old concepts.(More or less carriers have been the same, except larger since the "Super Essex" class of the 1950's.)
To compare ships in WC terms to RL ones.
Midway class- Concordia class.(Mainstay, and lasting up past larger newer ships.)
Forrestal class- Bengal class(TC varient) I'm tempted to lump her together with the KH as neither is really all that different.
Kitty Hawk class- I'm unsure what would be this equivilant. An improved Concordia class which is similar in build to the Confed class would most likely go here.
Enterprise class- Confederation class dreadnought. First ship to mount a specific weapon, large, mainstay, and symbolic.
JFK class(KH sub-class)- Confed class without PTC.
Nimitz class(expanded)- Vesuivius class. Very large ship, built upon principles of the previous classes.
CVNX- Midway class. New build carrier created in background of a changing political climate.(All previous classes were created during the cold war)