I don't think so.
Germany could have won if they were able to invade UK and secure the Russia border.
If London had surrendered, then the war would end
Would it, if the Commonwealth still stood and it were very costly for Germany to go around the world dealing with it?
Would Germany have surrendered if it had major colonies standing elsewhere in the world? And I ask this since we can't really solve this issue HoI2-style, with individual scripted events, tailored to each nation. There has to be a fluid mechanic which could reasonably work in all cases.
Here is what is wrong with this thinking.
I am Japan I attack communist China. They join the commitern so now I am at war with the Soviet Union. I am marching towards the Urals, there aren't any Soviet troops to stop me.
Meanwhile Germany is attacking and driving on Moscow. I would be happy to go back to the original borders, but I can't. The only way I can win this war is to take Moscow or hope that Germany does. Are you telling me the Soviet Union wouldn't JUMP at the chance for white peace?
Would Japan? Would Germany allow that kind of independent peace?
When entering one of the major alliances, you're committing with your partners for a total war. The system wouldn't work if anyone could just jump in and peace out independently at any time.
If you
could peace out freely, then at the very least it should come with a major negative impact to your relations with your former partners. Italy only did it because it was being overrun, and could only do it because Germany had its hands full at the time. And even then the country was pulled into a civil war between pro-Allies and fascists (which is something that could be modelled, perhaps, based off national unity).
In a winning context, the AI wouldn't likely make peace independently, and I'm not sure whether the proposed relations impact would be lesser for dropping out. Maybe, maybe not. Either way it would just be better to wait till the final peace conference. "Oh, but I
have to take all their territory everywhere," you might say, but that's less a flaw of the peace requirements than the AI. Normally, you should be able to sit tight, defend your borders and wait till your AI allies win the war, if you don't want to fight anymore.