But how is this going to produce an outcome any different than what occurred historically? All you are proposing is Fall Blau in another direction. If the historical operation couldn't defeat the Russians how is this new one going to do it?
Well, IMO because Fall Blau
and, more generally, an offensive along the Volga-Caucasus axises was the worst direction in which to attack in 1942. As the front extended along the Don and the Caucasus mountain range, more and more of the Axis troops had to be removed from the attack and allocated to flank protection. Thus, the "tip" of the German "spear" was weakening with every phase of the advance. The best illustration of this is that the German 2nd Army, used in the initial advance on Voronezh, was then effectively immobilised for the rest of the campaign and was of absolutely no use to the German troops fighting around Stalingrad. This problem, of a lenghtening front, was btw the reason why the Germans had to resort to use such a large number of second-rate allied divisions to plug the gaps in their line; without them, the advance on Stalingrad and the Caucasus foothills wouldn't even have been conceivable in the first place, to say nothing about its prospects of success.
The dilution of German offensive power during Blau
can also be illustrated by the losses they inflicted on the Soviets. As mentioned previously, barring the DoWs and the disabled, the Germans must have inflicted about 450,000 irrecoverable losses on the RKKA during July in the southern sector (excluding the Sevastopol surrender). However, Krivosheev puts at 995,674 the total Soviet irrecoverable losses sustained by the Fronts opposing HG "B" and "A" (again without Sevastopol) for the whole second half of 1942. This means that HG "B" and "A" inflicted 45% of the total Soviet irrecoverable losses for July - December 1942 in a single month, July, when they achieved their maximum concentration of effort. After that, Soviet losses dropped precipitously as the Germans allocated troops to flank defense and multiplied the axises of advance.
Why is an offensive northwards any different? Well, have a look at this map
. By going North, the Germans can greatly reduce HG "Mitte's" frontline by closing the Demyansk - Rzhev salient, which incidentally would probably result in a higher count of Soviet irrecoverable losses since it was the ideal target for a great encirclement. They can then drive northward in the direction of the Finns and Lake Onega (not shown on the map, but roughly where it ends), thus even more shortening the line, this time in HG "Nord's" sector. Again, this second phase would inflict large casualties on the Soviets - there is no reason to believe, in fact, that it couldn't inflict losses on the level of the opening phase of Blau
After that, Leningrad Front is completely cut off, about 100 kilometers behind the frontline, and can thus be finished off at will, adding another half-million irrecoverable Soviet losses. So, what's the final tally of this offensive? Maybe 1.5 million irrecoverable Soviet losses, more if you add the DoW and disabled, inflicted much faster than the 6 months it took to inflict 1 million irrecoverable losses in the original Blau
. A front shorter of hundreds of kilometers. The possibility to accumulate reserves for further offensive action and/or for a successful defense against a Soviet winter counter-offensive. Overall, a weaker Red Army and a stronger Östheer.