Thank you, gentlemen, for the insightful responses. Reading them, I concur that against good German play, it’s probably something that Russia can’t afford to do under most circumstances. However, if it can be done, perhaps a G2 Barbarossa might just be the scenario where it fits in, strange as that may seem. It all strongly depends on the situation after G1, of course.
Imagine this: Germany prepares for a G2 attack on Russia, and for that purpose, buys land units only on G1. Germany also takes France and kills the British fleet, losing a few planes in the process. In addition, a few German planes are sent to Southern Italy to guard against a British Taranto attack. The Norway infantry steps into Finland, and as many units as possible are generally sent east.
Now Russia puts absolutely everything that can reach it, in Karelia. That’s 11 inf 1 art 2 AA 2 ftr 1 tac – and of course this shouldn’t be done if the entire Luftwaffe can hit it, but it’s quite enough to deter an attack from Finland supported by only a few planes.
If Germany ignores this on G3 and continues the invasion and the drive to Moscow as planned, then Russia can take Finland with relatively small losses. A few British planes can be sent to support the surviving Russian units, if necessary. Next round, the Russians will take Norway. There’s a big German force moving towards Moscow, but the extra income will allow Russia to build more while Germany builds less. Germany may counter by building transports G3, in order to recapture Finland if Russia takes it - but it would probably need at least three transports, and that would be money not spent on ground troops. Depending on the situation, Russia may then either still go for it, or take Finland with a smaller force and send some units back to Novgorod.
Alright…. it’s probably a dubious plan, anyway.