@oztea:
So my point is, the value you are getting from the enemy NOT having islands to land on is that your forces in the rear areas can steam at full speed, and fuel doesn’t need to be wasted escorting them with convoys. Now in the game, the limits of air units movements represents this to a degree. But only for units we can actually touch. In reality, there are all sorts of things happening in the game that aren’t being represented with plastic pieces. Supplies are moving to your fleets at sea, while raw materials are moving back to your factories from far flung possessions. So the idea of awarding IPCs for control of worthless islands is not far fetched. We already have this happen with the Japanese NO for control of Guam, Midway, Wake, Gilberts and Solomons.
Yes, these are good points. Control of contiguous areas of oceanic space (and of the airspace above it) affects operational efficiency, which has economic implications, so it’s justifiable for this to be translated into IPCs to a modest degree even when the spaces contain islands with zero IPC value.
You could even take the concept one step further and extend it to contiguous oceanic spaces which contain no islands at all. The area I’ve marked in red on the attached map shows the contiguous areas of oceanic territory “controlled” by Japan at the start of the game, as defined by its outer perimeter of island possessions. Note that it includes some islands with an IPC value (like Iwo Jima), some islands with no IPC value (like the Marianas) and some sea zones with no islands at all (like SZ 18). This area could serve as a baseline. Each sea zone in the area could be marked (for the sake of visual convenience) with some sort of baseline marker – let’s say a white poker chip. The baseline by itself would have no IPC adjustment value. The IPC bonuses (and/or penalties) would come from gains or losses to the baseline.
Every SZ gain by Japan beyond the baseline would translate into an IPC bonus for Japan. (These gains could be marked with red poker chips for easy indentification.) This IPC adjustment would include SZs added to Japanese territory as a side-effect of an overall territorial advance. For example, a Japanese capture of Midway (in SZ 25) would have the side-effect of bringing SZ 24 into the Japanese perimeter, so the capture of that one island would translate into a gain of 2 SZs instead of just one.
Likewise, US advances into Japanese baseline territory (marked by blue poker chips) would translate into IPC bonuses for the Americans. There could be an additional bonus for the US (or an IPC penalty for Japan) if the US manages to pinch off and isolate parts of the Japanese territory; for example, if the US captures Okinawa while still holding Guam and the Philippines, the Japanese sea zones around Formosa and Hainan would be considered cut off from the rest of Japan’s oceanic territories.