It’s not. Let Germany do it. It costs the Allies less if they attack after the merger than if they try to block it because Germany’s air support makes any attempt to block a big loss for the UK. My purchase with the Baltic CV build is always 3 fighters for the UK and stack with the US fleet in sz8. If you are concerned about Germany attacking that fleet with the sz13 fleet+aircraft then you can block it with the Russian sub to save UK/US units for the attack on the German fleet if they combine.
Mm. Excellent, that’s what I often do as well.
If Germany unites its fleet, Germany can’t stay off the coast of Western Europe for long, because additional Allied reinforcements will easily kill the German fleet. The Germans either have to build an IC at Western Europe for immediate reinforcement (which uses a lotta IPCs, especially with added German naval/air builds), or the Germans have to go north or south. If the Germans go south, they get Africa and prevent the Allies from dumping from E. Canada to Algeria. But if the Germans go south, the Allies can feed infantry into Archangel, which means a really powerful defense at Russia. If the Germans go north, the Allies get Africa as described above.