Turns out I got some time alone with a computer while I'm here. . . 
I think you have a solid foundation to build on. A few initial comments:
Light Guns
One thing Grand Fleets struggles with is a the ability of light guns to inflict a disproportionate amount of damage relative to their actual effectiveness.
For the purposes of this game, I would either:
A) Drop them altogether
or
B) Make a rule that they can only cause damage against an unarmored target
A light gun should NEVER sink a battleship. . . but with the present rules, its certainly possible that they will if you get in close.
A is probably the easiest route to go, and given that the game is mostly going to involve cruisers, battlecruisers, and battleships firing at each other, I don't see that light guns will ever add much. Its an extra set of stats/rules for very little payoff. In a fleet level game, I'd suggest it needs to go.
As an aside - this is really something that needs to be fixed for GFII also. Destroyer flotillas and some battleships can pack a huge number of light guns. . . and with the current rules it can make them deadly even to well protected ships. Something needs to be done to rein them in significantly so that they are pretty much ineffectual against a major warship. . . as they should be. Again, dropping them altogether probably wouldn't cost the game much. . . but GF being a more detailed, task force level game has more tolerance for rules additionas than a fleet level game does.
Armored Deck
As written, the ability can give a ship a greater armor value vs. plunging fire than its main belt armor. "Armored decks" were somewhat less vulnerable than the standard variety, but were never up to the standard of a main belt.
This ability should either:
A) Simply negate the plunging fire bonus
or
B) Get done away with altogether. At a fleet level, the differences were not all that significant. Especially at the level of granularity that a d6 provides.
Which reminds me of something else. . .
Die Type
In many many years of gaming, I have never seen a miniatures game that didn't suffer when it was based purely on a d6.
A d6 does not allow for a sufficient variety in options, or gradation of statistics. IMO, you should definitely move this to a d10 based game to allow for smore subtle distinctions between different values.
Criticals
I think the expanded critical chart is the way to go. A 16 2/3 chance that a critical hit will result in a magazine explosion is a little excessive.
Listing
I love the rules for listing ships in GF. For this game I would suggest getting rid of the 50/50 roll though. At a fleet level game, simply getting a Listing result twice ought to be sufficient to capsize the ship.
Rudder
A jammed rudder ought to force turns, or prevent them, not simply cost additional movement points. That amounts to nothing more than a speed penalty, and doesn't allow for interesting historical situations like the Warspite circling helplessly in front of the oncoming German fleet.
Maybe when the rudder is jammed, roll a die.
1-2 Port
3-4 Starboard
5-6 May not turn
For every other hex of forward movement, the ship MUST make the indicate turn.
Magazine Explosion
I'd suggest putting the magazine explosion at the double six rather than the double one. Its more exciting to roll sixes.
Turret Superscripts
I get what you are trying to do here. . . there has to be a better way though.
I love the subject, and love rule systems. . . and this approach just makes my eyes glaze over and doesn't really help me visualize what is going on at all. I'd suggest giving this some more thought. Unfortunately, I don't have any helpful suggestions just yet. I'll let you know if I think of something.
Torpedoes
I must be missing something or my brain isn't working. .
What does the @number represent? Could you translate that notation element by element with an example?
Anyway, that's all I've got for now. Hope its helpful.
