Just to get a complete picture:
According to some earlier ‘studies’ I came to the conclusion that it is possible if Russia moves forward RU2,
that GE3 can destroy them instead of doing Sea Lion (bad mistake, Stalin). Russia has to wait moving forward untill after GE3 went Sea Lion of course and it has to buy fast units for this RU2 (mostly MECH).
This is possible even if GE1 or GE2 produced only land untis and invested ~70 IPCs into ships. The only question left for me, was if GE would subsequently be able to take Moscow as well. Apparently it can be done after this overeager Russian forward ‘gambit’.
Buying ships worth 2 complete rounds of production (total 98 IPCs) will  turn into a disaster for the axis if they also invade London. Almost single-handedly by the Russians! I’ve seen that too many times already to think GE can stop that.
No info on the outcome if GE produces this quantity of ships and still forgegoes the attack on London, but it seems to me that Russia and the UK are only to blame for themselves if Moscow still falls after these course of events (too much ships for GE).
In my experience (and assuming Russia does not make the mentioned mistake), it is already impossible for GE to take Moscow after spending ~50 IPCs on ships. Heck, even if they spend 100% on land units dedicated to march onto Moscow (although Russia then requiring heavy aid from the western allies), but that should be in a different thread and let’s not forget the dice can still ruin both sides. Although Moscow has a huge advantage in the luck-table…