I still think Subs vs planes should be improve, here is a less radical way.
Planes should be able to hit subs anytime they don’t submerge.
Subs on defence should be able to escape destroyers (in an other way than sinking all attacking DDs).
Subs should be used anytime (even when no DD is present) as sea-fodder casualties against planes to protect more important vessels.
If I kept the more important aspects of my last post:
1a) Planes only (without DD) can attack subs only naval group (or with transport) A@1.
c) After first round attack, all surviving subs can submerge in the same sea-zone.
2a) When planes only (without DD) attacks Subs+ other warships, Fg A3 StB A4, as OOB
b) However, the defender can now choose to sink Subs instead of surface vessel (contrary to OOB).
But, to do it, the defender must announce at the start of the first round that his subs are not submerging.
c)
d) After the first round, all subs can still submerge (as in OOB Sub Surprise Phase).
3a) When planes and other warships (without DD) attacks Subs only, all planes A@1.
b) All subs rolls, as OOB, a surprise defense strike @1 or can elect to submerge in the same SZ.
c) If Subs elect to submerge instead, only planes can attack @1 and it is played as in 1a above.
4a) When DD is present, all is played as OOB except all defending Subs can submerge after first round.
Subs on offence cannot hit planes.
But when there is only defending planes (against subs+ warships/planes), subs can be chosen as casualties (contrary to OOB).