Sometimes it can get a little confusing in island sea zones which units are in the sea zone and which are on the island. The statement is intended to make sure the attacker indicates which air units are which, since they can in many cases get to either space.
I say that the next game needs Canada, special neutral rules for Finland, and vichy french rules (and, depending on the time period, poland as well). Why be picky and only make a few improvements? :-D
I do similiar moves with China. I don’t allow any walk ins, I want a chance to kill an infantry unit in every territory Japan walks into. I’ll keep a mass (or as many as I can mass up) of infantry behind the front lines with the fighter as a counter attack force. If Japan can muster a ground force larger then I think I can counter attack and kill I’ll move my mass further back and to the north so ultimately it will cost Japan an extra turn of movement when China does die and they go after India. I’m always looking to counter attack. If you can get the Brits and China working together to keep Yunan from falling to the Japanese that’s great too, but, it really depends on how the game progresses.
I have heard people say they use major and minor IC’s in house rules. They just use 2 IC’s (maybe glue together) for major, and 1 IC for minor. We all have extra pieces to do it.