I don't know how the Wehrmacht prepared for Fall Blau in summer '42, but I think they got at least a few reinforcements and pulled some units from the northern front. They kept the Soviets busy around Rzhev (to suggest a threat for Moscow), but instead broke through the rather weak lines down south to capture some oil and industrial areas.

As Snake said, Para is in a much better position than the Wehrmacht was historically, so I guess the "A-A line" (Archangelsk-Astrakhan) isn't an entirely utopian goal for the winter '42-'43.

The main point until February is not giving up any important strategically important cities...