I think that the 2 Hit BB is too powerful when it is used in groups. Their self repair ability is too much of a benefit. Therefore, BB do not all repair themselves at the end of each battle.
The Rules –
1] The BB takes 2 hits to be sunk in a battle
2] After the 1st hit lay the BB on its side to indicate that it is damaged. It still fires as a 4. So far, no change.
3] After the battle is over, for each pair of “damaged” BB, the damage is concentrated on one BB which becomes “heavily damaged” and the other BB is considered “undamaged” and is turned right side up immediately. If there is an odd number of damaged BB, the remaining one BB is considered “lightly damaged”.
4] A simple rule would be to just let the lightly damaged BB repair itself, but the above Heavily Damaged BB are considered sunk.
5] A more complicated rule.
. . . a] The heavily damaged BB is immediately moved to the nearest SZ adjacent to a Home Country Industrial Complex. It is still laying on its side indicating that it is heavily damaged. A Home Country Industrial Complex is any original IC, except Hawaii if it is an original IC. It must not be one where there are enemy ships or a battle is being fought.
. . . b] During the place newly bought units phase of your next turn turn it right side up. It is immediately whole again and can be moved in your next turn after that.
. . . c] If it is attacked while it is heavily damaged it has just 1 Hit and defends as a 2.
.. 5.5] After the battle is over any odd/lightly-damaged BB are [at the owner's choice] handled in 1 of 2 ways.
. . . a] The lightly damaged BB is considered “lightly damaged”, it is immediately moved to the nearest SZ adjacent to a Home Country Industrial Complex and turn it right side up. It is immediately whole again and can be moved in your next turn.
. . . b] The lightly damaged BB is left on its side. It becomes a 1 Hit ship that is a 4-4-2.
Other rules for BB you can add –
1] Sorta like Subs can only hit ships, BB will mostly hit ships. A BB can never hit a CV, and therefore a CV can never hit a BB. A BB can only hit a Sub if there are no other ships to hit. A BB can only hit a plane if there are no ships to hit (other than CV which can't be hit or Subs which might be hit instead of the plane, see #2 below). Like enemy ships and Subs, enemy BB & CV can coexist in the same SZ.
. . . CV were faster than BB, never have a reason to get close to an enemy BB, and have plenty of planes to scout therefore, a CV should never be sunk by a BB.
2] If the only enemy pieces for a BB to fire at are Subs, the BB fires with a hit number of just 2. If there are only Subs and planes to fire at, it still is a 4; but the player who owns the piece hit decides which piece he will lose, plane or Sub.
. . . The BB is not great at sinking Subs, only its escorting DD can do that. Most BB were good at shooting down planes though. This rule makes DD the best ship for sinking Subs, but planes are better because they can't be hit by Subs.
3] BB join with Subs to fire in the 1st fire phase of the 1st round of a battle, not in every round. Other ships can take the hits from these pieces. Ships sunk by BB & Subs can only fire if they can fire in the 1st fire phase [except DD which are sunk by Subs can still fire, and BB sunk by Subs can't fire]. Subs may get 1st fire in every combat round.
. . . The guns of BB had very long range this ought to give them 1st fire. Subs were sneaky.