@Narvik:
Since the cheapest unit always will be fodder, why not just change the cost ?
Destroyer cost 8, A2 D2
Submarine cost 10, A2 D2 and submerge
Tranny cost 9
A challenging idea which should be explored, there was a time when Sub have A2 D2 and cost 8 with a few different abilities.
You only add submerge, did you imply that surprise strike should disappear?
My first impression, is that doing this makes 2 basic naval units with same attack and defense factor.
The historical background seems to show that submarines were cheaper to built and weaker against Destroyers.
Making Subs at a higher cost seems a bit counter-intuitive, on a ship for ship basis.
However, this could be rationalize by saying that there is many more Sub vessels represented by a given sculpt compared to the Destroyer.
Even though, the fodder problem will be only partly resolve.
If the opponent have many planes, even with a higher cost, the owner may see that Subs can be sitting duck compared to Destroyers. So wasting the costlier subs, instead of losing the more cheaper but useful Destroyer.
Most of the time, Submarines will be taken second in order of casualties, keeping others costlier warships as the last units.
This will only displace the historical issue. Since in major naval battle, subs were not the main target and casualties.
I know that my casualty rule for submarine contradict the usual pattern of casualty, this makes submarines a less interesting buy.
However, I think this could be compensate with a more elusive factor against Destroyer (1:1 to block submerge, for a single round, and surprise strike, as long as a Destroyer is present on 1:1 basis. As DK suggested.) And/or by making Submarines more dangerous somehow? Just too bad that A&A 1942 version have no Convoy disruption rule. That was the main function of the submarines. At least, it could work in Global versions.
My casualty rule for Subs still keep an OOB specific game strategy (mostly used by Germany, but not exclusively), attacking with planes and Subs against carriers, destroyers and planes escorting transports.
This allows the attacking player to sink the cheaper subs and keeps his costlier fighters.
That’s the big difference compared to a more radical casualty rule such as : “Subs must be the last casualty amongst all combat units.”
The only particular situation which can arise after a few combat rounds will be Fighters and Subs attacking the remaining Fighters of such a fleet. In OOB, the attacking Fighters must be selected as casualty.
With my rules, the attacking Subs will be chosen first.
This is no big deal since this situation is OOB usual in ground combats or against any other warships.
In addition, giving back a combat value to Transport would probably balance the change for Subs casualty, because the DDs, Cruiser, Carriers and BBs will be more exposed to direct damage than OOB, lowering their odds of survival.
But, considered as a whole fleet, with Subs and Transports able to give and take hits at the end of the battle, this can gives a similar odds of survival than OOB.