This would be in line with the land battles, but 2 rounds might make more sense. Would give you a better chance to clear a sz for amphib etc…… After the first round of battle the attacker can either continue his attack, call off attack and stay in the contested sz, or retreat. He can retreat part, all, or none of his ships, but if he decides to go a second round then he can’t retreat anymore (sz is then shared/contested if both still have ships).
Subs need to have better survivability if they submerge. There wasn’t much sub detection going on in WW1, so why can you roll 3’s and 4’s at subs to sink them so easily. I would be inclined to say if a sub submerges that you must roll a 2 or less to kill it regardless of the attack/def value of the opponents ships. It would be easy if multiple types of ships are attacking only subs, attackers would need to roll at 2 or less to kill a submerged sub (one round to do so). If there are multiple types of ships on both sides, it could take some thinking, but would still work (I think). Have the attacker roll out all his attacking ships (dice), and note the hits, and how many 1’s & 2’s were rolled). You still allow the defender to choose casualties, and higher rolls (3’s & 4’s) that hit are applied to surface ships. He then applies any roll of 1 or 2 to his submerged sub, or to another ship if it is still afloat (his choice). If the sub doesn’t submerge, then higher rolls that hit could be applied to it.
Say 3 UK ships (1 cruiser, and 2 BBs) are attacking 3 German ships (1 BB, 1 cruiser, 1 sub), and the Germans sub submerges. UK cruiser rolls a 2, and the BBs roll a 3, and 4. The 3 and 4 can’t be applied to the submerged sub, so those hits go to the bb (still has 1 hit), and cruiser is sunk. The 2 rolled can be applied to the submerged sub, or finish off the bb (def choice). All the attacker dice that got a hit must be applied if applicable, but if he doesn’t roll a 2 or less the submerged sub can’t take a hit (survives).
Need to expand the sz’s that can be attacked for econ damage. USW against UK should be allowed in any sz that touches the UK/Ireland, or Canada, plus the 3 Med sz’s (16, 17, 19). If German subs are in sz 2, 7, or 8 then you will also be raiding the USA (you can also raid sz 1 for US only). Subs roll for damage during the victims collect income phase (like OOB); roll of 1-2 cost 1 IPC, roll 3-4 cost 2 IPCs, roll 5-6 no damage. Track total damage through the turns, and any time the US gets to 3 damage (3 strike rule), or the UK/US collectively gets to 10 damage then the US can declare war (damage could be something like 8 for UK 2 US, or just 10 UK).
Need to either allow German subs to be mobilized in friendly ports (sz 18 & 20) restricted to one sub per turn, or allow Austria, and Turks to raid the Med sz’s.
Something else to think about Blockade:
During Germany’s collect income for every surface warship the UK has in sz 10 or 11 roll a dice. Roll 1-2-3 deduct 1 IPC from the German treasury, 4-5-6 miss (deduct nothing). I know that Germany never got to blockade with their surface fleet, but in this game if Germany manages to get naval dominance around England allow their surface war ships to blockade any sz that touches the UK as well.