I would imagine your Allied opponent would notice the movement west and take appropriate actions. In my example, after a mIC on UK1 and then you move ground troops back west on G2, I could build defensively on UK2. But then you leave yourself vulnerable to the Soviet counterattack. I think moving your German ground troops back and forth like that on the first two turns weakens any assault you may have.
IMO if you attack the Soviets G1, you have to table Sea Lion until you have the eastern front well in hand. But I’m sure there are some that will refute that.
G2 usually ends with London factory max bombed by 3-4 bombers, so that’s less an issue. So the U.S. presumably won’t be rushing units on US1 to get to London, and UK2 will only have 10-15 ipcs to spend on defense. That means London should have about 5 AA, 7 inf, 1 mech, 1 tank, and 2 fighters, then whatever UK buys with 15 ipcs, so the move should mean they’ve got 1-3 fewer inf and 1-2 fewer fighters
So here is what Germany ends up with: You take 6 or 7 inf from Norway/Finland, 2 inf that started in Denmark, and 2-3 from Germany (who move to Poland on G1) so Germany still has about 15 infantry in Romania/Bulgaria at the end of the turn (depends on Yugoslavia attack/retreat), and only 2 art and 2 or 3 tanks.
But Russia doesn’t know about Sea Lion on R1, so not sure how aggressive they’d be. That’s what I’m thinking through… a 6 tank buy might be their best option but they’re not attacking German territory until R3 for sure. A still strong U.S. Atlantic buy and Russian tanks might be the combo that means its a truly terrible idea.
You really do risk ceding Finland/Norway to Russia and Italy has to commit to the Russian front.
But… you take London G3, and G5 you have 10 or 11 transports to retake everything on the Baltic sea: Norway, Finland, Novgorod, Baltic States, and Poland.