Well, throwing everything into Russia might work, but I think its riskier than you envision. It is very difficult for Germany to take Karelia early unless everything is thrown at it. In that case, the remaining German armor is vulnerable to a UK, USA, USSR triple counter attack before any reinforcements may arrive. This is so because there Germany did not sink the UK, USA fleet at a low cost while the opportunity existed AND THIS OPPORTUNITY WILL NEVER EXIST AGAIN WITH DECENT ALLIED PLAY. This effectively speeds up the allied reinforcement of Russia, and makes the defense of the rest of Europe very thin and will probably remain so the rest of the game.
Even if Russia falls to Germany, under this scenario the allies are not out of the game (assuming 82 ipc are not taken). Europe is left defenseless with very little counter attack potential by Germany as everything has gone into Russia. France, E. Europe, Karelia may be taken almost immediately by good allied players (perhaps even before Moscow falls !!!). How then will Germany protect both Berlin, Moscow, and Rome :-? ? Berlin must immediately be reinforced as without the capital, the game is over for Germany. Germany must also reinforce Moscow from a possible Allied attack through Karelia, at least until Japanese troops can arrive to reinforce (else what has been gained)? This leaves very little $ available for attack casualties to retake France or E. Europe, even with the money gained from Russia, but Germany must do so to protect Italy.
In games I have played, as Germany I will build first until the point is reached where the allies start to send troops into Karelia via Finland. This is when I decide to take Karelia (but only with good play by Japan) to prevent a combined allied defenses (fighters excepted of course). The reason I do this is because Germany starts out with a larger economy than Russia, and the German economy grows (via African $) while the Russian economy shrinks (via Japanese victorys in Asia). Germany must present the maximum LONG TERM threat to Karelia/Moscow to allow Japan to conquer most of Russia. Then Germany and Japan must crush Russia between them. IMHO, this is the best scenario for an Axis win.
Any other thoughts on this?