The reason I thought of it was in AA50 when Japan is contested in the sea, she tends to stick close to the asian coast. It is atleast 2, probably 3, turns away from the US and only 1 from Japan. As far as cost, just look at it as 15 ipc a turn for 3 turns, turn 1 navel base, turn 2 IC in fic, turn 3 air base. I can really see a declare war turn 2 or 3 working well with this and a smash china/india tactic. Once your back is safe, then japan could start moving in on Australia. I just know as the US i’d hate to attack a jap fleet with 2 or 3 carriers, a battleboat, and say, 10ish planes that can hit me if i’m within 3 squares of it.