@tinfoil666 I was thinking we could do territory highlights of territories eligible for placement (you can demo the 'territory highlight' by doing a find territory, it will outline the territory in white). We could potentially turn the territory highlight on for all eligible territories, then when the territory/factory is exhausted, turn it off. I wonder if combining that with grayed out factories would make it even more clear.
I like the territory + factory visual change.
If there were only 1 implemented, I would pick factories, but on maps where the factories are 'invisible' (such as the 'build anywhere' maps), then you would need to highlight the territory for this to work.
Until your response, I forgot that the factories are not always visible.
 Don't forget that the 'eligible territories' should include sea zones adjacent to factories with builds left. Ideally, the sea zone highlights should cease once you have placed your last sea unit.