Allow Subs To Surface in PG/AG

"Man the 88!"

Most WWII submarines were usually surfaced, had deck guns, and used them. It's easy enough to create a separate "mirror" unit of the sub with surface attributes and use a scenario editor to assign a surfaced sub as "transport" to the submerged sub, allowing simple toggling back and forth during play. The surfaced sub would be faster and have surface/AA gunnery but would not be classed as "submarine" so it would lack the submerged evasion ability and any unit can take a shot at a sub caught on the surface:

The examples below assume visual spotting range (radar/sonar could change things). First note the submerged sub's movement and 1-hex spotting range (periscope depth). It is unable to attack the land units but is immune to their attacks and has a chance to evade against destroyers and tactical bombers:

The surfaced sub has greater spotting range and movement and can engage in surface gunnery duels with the land units but any unit can attack it and "evasion" must rely on its initiative and combat to avoid damage:

These exact numbers are provisional. A Type VIIC U-Boat would have lower speed and gunnery than a US Gato class, or you could stick with a generic sub.

U-boat men at the gun (1917):