Ok, so you want to attack the 3 most important neutrals as axis at roughly the same time early in the game for strategic/econ purposes, maintain pressure on Russia, and keep the Anglo’s off your newly acquired territories. Pretty big task lolWhat do you want the UK to do on the first couple turns? When do you want to bring the US into the war? You want to set-up and do Barbarossa to keep things looking normal and get to Moscow (axis goal). Should you set-up to hit the neutrals G2, or G3?
4a) Take Turkey to give the axis access to the Middle East and Southern Russia (income/strategic value).
4b) Hit Sweden for more income (easy enough), and probably Switz so the allies don’t ever get 2 free inf.
4c) Take Spain and set-up some kind of def/counter attack (or naval attack), because this is where you are going to be most vulnerable.
1 (UK) - You want the UK to build mostly inf UK1 (no IC in Egypt), so maybe buy 1 ship G1 to lightly threaten Sea Lion, or save most of your income? Sounds crazy, but you probably want the UK to do Taronto so you can kill the Med fleet leaving the UK fewer resources at their disposal to threaten Spain and Turkey.
2 (USA) - Have two choices, both have pro’s and con’s.
a) Leave USA out of the war until they come in on their own and cant preform attacks until US4 (may even entice the UK to attack Japan so the UK tie’s up more resources in the Pac still leaving the US out in the cold?) This will give the Euro axis some time, but the allies will be much stronger when they do come over and could build mostly Europe from the start
b) Hit US navy hard G1/J1. G1 attack sz101 w/German sub to try and kill cruiser/tpt. J1 hit both the Phil (fleet and island), and destroy US Hawaiian fleet (making sure the main Japanese fleet at Wake is safe from counter attack). Also hitting Britt BB etc… again leaving UK w/fewer resources. This sounds strange bringing the US into the war on the first turn when planning for an axis neutral invasion, but the US will be hard pressed to build in the Atlantic because of Japanese aggression. If they build Pac for the first couple turns in response, then you won’t have US ships sitting in sz101 able to hit Spain for a few turns (easier to def for the short term anyway).
I’m assuming you will still set-up and invade Russia G2 (or G3) because you don’t want to tip off the allies, and still need to take Moscow.
When to attack the neutrals G2/G3 or It2? Depends on if you have the use of the German air force on G2, and the Luftwaffe will probably be needed to take out the UK Med fleet G2 (more risk to your mechanized units vs those inf stacks w/o air power). Also who takes Turkey or Spain and when? The Italians could take Greece It1, and be ready to invade Turkey It2 (after the Anglo’s take their 2nd turn) and Germany moves in reinforcements G3. On the other hand Italy could take S France It1, and be ready to invade Spain It2 and the Germans could land some ground/air on Spain G3. In this case the Germans activate the Bulgarians G1, takes Greece G2, and invades Turkey G3 (hides intent). Either way I think Italy takes one, and the Germans reinforce it, then and invades the other (along w/Sweden of course). This allows the axis to basically go back to back and disguise it somewhat. Plus if the Germans hit the neutrals G2, the Americans would surly build Europe on US2.
As you described one of the main problem is that if you take Spain you will have yet another coastal territory to defend, and stacking it isn’t really a good option. Setting up a counter attack from Normandy or S France is a risk because again your units are on the coast and the allies could probably hit either of those territories and kill off your units by sea from Gibraltar. Even setting up mechanized units in Paris could be problematic because the allies could cut them off by taking Normandy and S France. Attacking the combined allied fleet would also be costly, and if it fails the axis are doomed if they lose the bulk of their air power.
I’m not advocating that the axis invading the neutrals early is a good strat, but if I were to attempt it think I would try to take out as much US/UK fleet in the first turn as possible (and turn 2), and try to disguise it best I can. Get the US building in the Pac theater the first couple turns would be key, to keep them out of Europe till like US5?. If they have to start from scratch on the Euro side on say US3 (after you take Spain etc…) then you could defend Spain for a couple turns before withdrawing forcing the US build more before coming over (either more ships, or more ground). Put some pressure on the UK so she builds mostly inf on the first turn, and make sure the UK Med fleet can’t interfere or be used to re-take my prizes (on the bottom of the Med would be the best place IMO). I think I would have Italy take either Spain or Turkey on It2 (Germany reinforces G3), then have Germany take the rest on G3. Need to watch what Russia has in the south because you don’t want them to be in position to counter attack your units in Turkey. Don’t think you can afford to delay Barbarossa past G3 though. Japan should also be ready to kill some Mongolians on J3 if they haven’t already activated them (breaking the NAP and turning them Russian).
Look at my Afrika Korps strategy where I answer all your question!