I agree this game must be kept as simple as possible (KISAP) and NOT simple stupid (KISS) like the Risk game. It is obvious we need some special rules, like a sub can not kill aircrafts nor shore bombard land units, even if it historically had a little gun on deck. This is logical.
I think IMHO that the naval rules from AA50 is the best so far. Of course it look strange that one single destroyer will allow bombers to kill hundred subs, butt if we had to match destroyers and subs one-to-one, just imagine the more complex resolving of battles.
Now gimme a + and help me reach the 800