While not all ships featured in NavyFIELD were actually laid-down, let alone saw combat, even those that were not were 'planned' for production during, and for the purposes of fighting, the war.  Germany's 'project' ships, for example, were part of Germany's "Z" plan; an ambitious naval expansion which Germany, prior to the war, had hoped it could complete with (of all things) the assistance of the British.

The British are, remember, a partly viking (a.k.a. Aryan) descended nation, and Hitler considered them to be racial kin of the Germanic tribes; fated allies, he believed, in his prophesized struggle against bolshevism.  The political climate in Britain had certainly not been sympathetic towards the Soviet Union in the years leading up to World War II, and a different/more temperate German leadership, one which less antagonized British pride, might have been able to win British favor in forming an alliance against possible Soviet aggression in Europe.

Imagine then, what had this been the case?  Would British naval attaches have been present and applauding in Hamburg as Germany launched the first of its "Z" plan's super-battleships?  Would Britain have turned a blind-eye as Germany, under an artificial pretext, invaded their common ancestral enemy - France?  Would they then-have been allies in the struggle against the Soviet Union in the West?  Could the U.S., similarly fuelled to support anti-Soviet regimes by its strong German minority, have - far from imposing an oil embargo - offered a lend-lease program to the Japanese Empire (to assist against Soviet expansion in the East)?

Would World War II's historical enemies, Britain and Germany, the United States and Japan, then-have fought in side-by-side against the Soviet Union in Atlantic and Pacific respectively?  This is purely hypothetical, but emphasizes the sort of scenario(s) that NF encourages you to explore.

Keep in mind that Akagi and Kaga were intially laid-down as a battlecruiser and battleship.  Still under construction, they were built 'into' carriers following the signing of naval treaties which outlawed the ships they would otherwise have become.  At the time, the full potential of aircraft carriers had not yet been realized, and so naval limitation-treaties focussed primarily on limiting the number, size, and capabilities of the big-gunned ships.  Under the tearms of the treaty, the Mogami class, for example, were armed with six-inch triples.  In anticipation of war, however, the Japanese had designed them to 'accommodate' an 8-inch double (with which they were rearmed at the onset of hostilities - hence, the Mogami CL and CA remod').