The cleanest approach would be a completely new engine. That is not a starter.
That leaves us with the existing game engine. With sufficient effort it could be modified - less effort than a completely new engine but would not eliminate totally the basic interchangeability of the existing game design.
With sufficient development resources I would modify the existing game engine along these lines which I privately raised with Bullwinkle58 some 7 years ago. What follows is a very abridged summary of what I discussed then.
I would introduce the concept of currency into the game. Currency would be a new industrial production (like resources, oil, manpower etc) based on the respective GDP. The simplest approach would be to make it related to manpower centres. The game world would be divided into 3 currency blocs; the American dollar, pound sterling and the yen. Each bloc would maintain its own global currency pool. The yen bloc includes the existing IJA and IJN nationalities, the $USD bloc includes the existing USA, USN, USMC, Philippines, French and Chinese nationalities, the sterling bloc includes the existing British Empire nationalities and the Dutch. This roughly equates to the historical division of logistical maintenance which occurred.
The existing game logistics would be retained but the additional layer of currency cost would be attached. Thus when purchasing replacement aircraft not only would you need to have available onsite the existing requisite supply cost for the airframes but also sufficient currency in the global bank, sterling if purchasing a British airframe (or Dutch/Australian/Canadian etc), yen if purchasing for the IJA or IJN.
Production of supply, manpower, oil (representative of GDP) would generate currency. When surplus Australian supply is sent off to American bases this export would be purchased by the Americans spending $USD at a fixed exchange rate to sterling thus the $USD global bank would decrease and the sterling global bank would increase. When fuel was imported into Australia from the West Coast, sterling would be spent and $USD earned respectively.
No longer would it be feasible to simply rely on American logistics. British Empire industry would need to be kept in full production and exports generated to pay for logistics. A too hasty Sir Robin would too quickly give up production capacity and impede the purchase of devices for LCUs, airframes, rearming ships (currency based on ship nationality) etc at a time when the global bank would be low on the relevant currency. Conversely Japan would need to widen its horizons as to the necessary industrial capacity which should be targeted in its expansion phase.
Of course the idea is more complicated and nuanced but the above should indicate the potential.
I like this. One complication with charging for moving supply would be double/triple-charging if Supply* were not tracked more closely. Supply moves around very freely in the game now (the automatic movement, I mean) and that mechanism would cause the new charging scheme to fail if, for example, the movement of Supply to a base of a different nationality resulted in a charge. The consumption of Supply might be a better point for the charge. That would be imperfect too, as 'free' pre-positioning of Supply could still be done, but would be more in harmony with current game mechanics.
* Supply meaning each of supply, fuel, resources, oil.
It would remain an abstraction, thus not perfect.
Auto overland movement of supplies would not be captured. The emphasis is on the point of "purchase" of supplies. Thus eating food and drinking water would not entail a purchase. Luckily the game continental land masses roughly fall within a single currency bloc. As a by product greater consideration would be required as to which nationalities would conduct land offensives. The common AE Allied praxis of sending several USA/USMC divisions to India, which never did occur historically nor could ever have occurred in real life would have consequences. The least being the likelihood of having to spend PPs to turn recaptured Indian bases from American to British control.
The actual export and import of material involves conscious player decisions based on the need to generate "foreign exchange". The existing underlying logistics rationale remains. Currency at the point of purchase is merely added to the current model. Have a healthy bank balance surplus, the pressure to export is reduced. Have a poor bank balance, those idle merchantmen will need to be used to carry material overseas to earn that foreign exchange.
Interesting. How much would it cost to convert HMS Victorious to use US planes, as done historically?