The idea of IL, is not to give scripted strategy or force player to do “historical” things. The idea is bound to geography (or maybe geo-policy).
Why Japan attacked USA at Pearl Harbour? For having free hands in conquering Philippines, Indonesia, Borneo, etc. And why? Because there Japan could found: oil, rubber, metal ores, etc. They are not after cities. And they are also not after capitals. They look for economic resources and strategically relevant territories.
So the war effort should be aimed to conquer key territories on the map that gives economic benefits, while at same time negating them to the oppoents.
With a wise allocation of economical objectives that bring victory for the side that conquer them while cripple the oppoennts economy, player have to devise strategy to achieve goals that go in the direction of promoting operation all over the map.
Another thing, that I have tried to do as an home rules, is victory based on collecting victory points. Each turn a natio ncollects victory points based on the control of key strategic and economic territories on the map. Increasing of such points is the measure of the strategic and economic advantage a nation is achieving while at same time having less point collected “simulate” the moral factor of a nation that may give up in a fight if continually defeated for the control of strategic key points or economical resources or national territories.
So the victory conditions should be individual for each nations and composed of several factors: economical (IPCs), strategical (control of key territories), moral (bringing war in the enemy territories while preserving own territories). Each end of round victory points are given to each nation for the obvjectives achieved. Victory is gained reaching X victory points, with the additional constraints of having an advantage of Y victory points on the other side. (having less then Y victory points allows the war to continue, the advantage is still not decisive).
I know, I have gone too much off topic but what I would like to have is a of assessing the winner, simple (counting victory point at the end of the round is not too much complicated) but also bound to the geography and policy of the wolrd.