I am not a campaign guy. Other then some testing I have not really played one. I'm not interested much in playing against the AI. As I noted in a private e-mail I think your letting yourself in for a ton of work. That said though what you have here looks interesting to me. Since MP play is my thing I'd much rather be an on-line player in your campaign, then a campaign commander.
I would suggest that capitol ship refit times be thus:
Lightly damaged 1 week
Moderately damaged 2 months
Heavily damaged 4 to 6 months
This really hurts and will give both sides pause before they decide to keep a damaged ship in the line rather then send it home to fight another day.
There is no good way to apply the ACH option as any combination is unfair to someone, in some way. From the German view I don't think it fair to leave the chance to blowup up an English ship completely off the board. Without it the war at sea is simply a battle of attrition which the KM is unlikely to win. I prefer the variable ACH idea so that neither side will fight the battle in accordance with any set ACH option. Somehow a method has to be found to press both sides to be aggressive, yet give each something to fear. The beauty of fighting battles in the context of a campaign is that politics as well as strategy and tactics, are in play. So any successful, and unpunished, KM Op will cause great concern at the admiralty, while any loss of a KM capitol ship will give the Kaiser severe distress.
I also think that not allowing the RN side to play the long range battle tactic is opening up a can of worms, and could cause some unpleasant disagreement between KM and RN players. If your the RN fleet commander at what range is considered gaming the system? If a certain range is set then we are back to the unrealistic (as you note) precise control of ones fleet to stay just inside the accepted range.
I would suggest that Tactics not be limited but that the on-line player commanders, (Jellicoe, Beatty, Sheer, and Hipper), and anyone else who has a big ship command. Not use the Micro view map while fighting the battle. This will go a long way toward preventing the precision range dance that we both abhor, and would allow both sides greater ability to apply tactics to any given battle.
If you can pull this off, perhaps a campaign primer could be written on how to do MP campaigns in the future. I'd be happy to help out in any way I can.
Regards ANav