From: Utopia Planitia Fleet Yards
Taking every island in the game without needing ships to supply them is off.
I think this is exactly the point. You want to invade an island, India, Australia, you can. But, you will need to have the needed ships to supply your armies there.
And, of course, with the losses, you will need to build ships for your supply network.
People seems to complain that Japanese can go too far away and too quickly. Well, if they don't have ships for supplying their armies, their islands, they won't go too far away.
USA won't have this problem. They will have the ships later.
That's the way I would solve the current balance issue. Add the usage of transport ships (as before) or MMs to perform port supply and not a fix amount of ships, an amount based on the size of the port. With supply interdiction of subs, or surface fleets, transport ships or MMs will be lost.
At the end, a crippled MM fleet will no more supply some islands, that could be ignored, and there is the island hopping.
Chancellor Gorkon to Captain James T. Kirk:
You don't trust me, do you? I don't blame you. If there is to be a brave new world, our generation is going to have the hardest time living in it.