El-Phil writes:
"Well you wouldn't need full DNs everywhere, just in your main fleet(s). There would be smaller ships for anti-pirate duty, convoy escort, etc."
Perhaps. On the other hand, there's something to be said for having one ship that can fill BOTH roles vs 2-3 that can fill only one, and then only against similar-sized ships.
"...your aren't going to waste space on a ship of the line with too much anti-fighter weaponry are you."
Depends. In strategic combat, with its brain-dead AI, there's no guarantee the anti-fighter/missile ship(s) will always be where it's needed (e.g. it could be dead or out of position).
"For ships of the line, if you want to use the Royal Navy system then Dreadnought is big primary gun only while Battleships have primaries and smaller secondaries for taking out yappy things."
Actually, it seems BOTH the primary (12 - 13.5 inch) and secondary (6 - 9.2 inch) batteries of pre-dreadnoughts were intended for the enemy's battleships, with the tertiary battery (3 inch and below) targeted on "yappy things" (LOL) like torpedo boats. At the expected engagement range of 3,000 yards or so, the secondaries would theoretically shred the lightly armored parts of the enemy battleships while the heavy guns delivered the death blow. In practice, however, the shell splashes from the secondaries tended to interfere with spotting for the big guns. Moreover, after the Battle of Tsushima, where much of the firing was at two to three times the expected range, it was recognized that the secondaries would be ineffective at "modern" distances. Dreadnoughts of the early 1900s basically dispensed with the intermediate guns and mounted a secondary battery (6 inch and below) for torpedo defense. HMS Dreadnought herself was built with 18 12-pounders to deal with "yappy things".
Reference:
http://www.gwpda.org/naval/pdredmdg.htm
As I've read on this forum, the SE IV strategic battle AI also has something of a problem handling ships with mixed-range batteries. I've even seen this myself in a strategic battle with a TDM AI. Each of the AI's BCs, apparently using a Max Range strategy, closed to the range of its single range 7 weapon (shield depleter?), ignoring its three range 6 weapons (acid globule?). After an ineffective enemy salvo, my own BCs (also Max Range) closed to range 6 and fired 6 PPB V each. The 6 to 1 exchange of fire essentially decided the battle.