I'm now looking at helping to add the extra WW2 units to CTP for Fires and I have a question which someone (and I'm looking at Chrome here

) might help me with:
Some units have had their resource requirements removed in CTP such as bombers, fighters, tank, carriers etc who all use Oil in Vanilla. Even though I understand that the air units would only use a small amount and therefore stands to reason that it should be removed, I'm not sure about the tank side of things and I also don't understand why oil has been removed from the Carrier but not the Battleships.
I need to understand the logic behind this so that I can follow the same logic. I don't want to say too much to avoid spoiling what I'm doing (happy to discuss via PM in more detail though)
Also can you have 1\2 resource utilization? That might make things a bit more realistic at least for tanks. Potentially we could do 1\2 oil per tank and 1\4 for air units?
Another point is that we could use Iron as a resource requirement for standard industrial naval units (not replacing the Aluminium ones which are the later units). Considering Battleships and the like are large units and would potential use an entire resource and usually by that stage iron isn't really used (well apart from the monopoly pre-req buildings.)
Let me know what you all think.