If you build two carriers with the Germans in SZ 5 then you are saying that the Allies need to throw themselves upon the German fleet in SZ 5 to win. Otherwise, why would you advocate spending nearly an entire turn’s income on Aircraft Carriers and tying up 67% of your fighters in SZ 5?
As for the 8 vs 12 unit threat. I really don’t see 12 units being a viable threat from England. They can only build 8. That means to get 12 they have to plunder their stacks somewhere else which means less forces there for a minor addition somewhere else. Honestly, since Germany’s already planning for an English followed by American assault, the change is very minor to include the addition of 4 more British infantry. What, you need an extra 1 or 2 infantry of your own in W. Europe? Not exactly a game breaking diversion of forces in my mind. But that’s my opinion of it.
Meanwhile, you’ve spent 16 IPC on transports. You’re also probably out of Africa because you were buying transports, not ground forces to liberate it, which means you have less then 25 IPC a round income, maybe worse, but you might be reclaiming some of Africa but down Australia, New Zealand, Madagascar, Persia, T-J, Egypt and India. So let’s just say 25 IPC.
That means to fill 4 transports you are making 7 Infantry, 1 Artillery. No tanks. To fill 6 Transports you’d have to take infantry/artillery from somewhere else and spread yourself very thin.
And if you had all your lands and more, then why would you need the 16 IPC in transports when you could put an IC in E. Europe or Norway cheaper and almost as efficiently?