Wheatbeer, I am happy with the Collaborative Neutral Blocks rules.
Saudi Arabia would be a good place for an American minor IC when the Axis invade Turkey.
Also like the neutral navies and air forces and the 3IPC propaganda cost for American imperialism.
As for who controls the neutrals and their navies/air forces, I would suggest Italy for the Axis side and France for the Allies side if for no other reason than they come last in the turn order. So if turkey is attacked, the ships in z100 become French.
The only other piece I would like to suggest is a further deterrent to invading spain or turkey:
Sweden and Switzerland
If any Allied power attacks any territory or warship in the Iberia Block, Sweden and Switzerland immediately become pro-axis neutral. If any Axis power attacks any territory or warship in the Islamic Block, Sweden and Switzerland become pro-allies neutral.