The possibility of an “economic alliance” would not occur overnight in the 1930s. Like that “military alliance,” it too is another ‘what if’. And there were people in the Western Europe and the US at the time who thought the Soviets and the Germans were going to pursue those alliances.
For the economic alliance, there was a 1938 research article by a Dutch researcher, based on economic data from the US Treasury Department, that German-Soviet trade relations could lead to the foundations of an “economic alliance.” Although a promising prospect, the author of that report also cautioned that it is still too early to speak of one and that the two countries would need to work further to realize it. The economic alliance would have to require more effort from both countries to achieve it, but the possibility was still there in the wake of the Anschluss.
The research article in question is entitled “Russia’s Trade with Germany”: http://www.jstor.org/stable/45335542
Given that conclusion, I am convinced that if the Germans and the Soviets were to somehow find a workable solution on how to divide their spheres of influence in Eastern Europe, that alliance needs to be fully achieved no later than the 1940s. The real problem, which I am glad you mentioned, is how long would this economic alliance last? Was it incorporated into the Molotov-Ribbentrop Pact and eventually broken when the German Reich invaded the Soviet Union? What would be the point of splitting Eastern Europe into German and Soviet spheres of influence and forging those alliances?
The other research I found stipulated that the long-term aim of German-Soviet rapprochement and those alliances is to implement a détente between the NSDAP and the CPSU. That détente may or may not have occurred in the 1940s. If anything, it is more likely that the détente would probably happen between the late 1940s at the earliest or the 1960s at the latest. And granted, this is assuming the NSDAP and CPSU both realized that their expansionist aims do not lie in Eastern Europe but across the Eurasian landmass.
Why would the German Reich pursue détente and refrain from declaring war on the Soviet Union? It is true that there were factions inside the NSDAP that believed the German Reich should expand eastward, but their contention was the precise boundaries of the German sphere of influence in Eastern Europe. Would it be something close to what I had outlined in the previous comment? Is it everything west of the RSFSR (Russian Soviet Federative Socialist Republic), including Belarus and Ukraine? Or, as post-1945 historians assumed, is it everything west of the Urals?
These questions cannot be properly ascertained without us also realizing that, in addition to those factions, other factions within the NSDAP believed that the German Reich should retake its colonial holdings in Africa. That brings me to Hermann Göring, who is cited in the available literature as having some vested interest in promoting rapprochement between the NSDAP and the CPSU. If the German Reich is going to regain its African colonial holdings, his thinking went, then there needs to be rapprochement with the Soviet Union. The long-term stability of those colonies will require a détente between the German Reich and the Soviet Union.
The evidence you cited is copacetic with that conclusion, Bogumil. Göring knew that because of the German-speaking world’s geographical position, the German Reich cannot afford to experience another World War on two fronts. He was also of the view that the German Reich was better off pursuing broader foreign policies that pertained to Africa and Asia (where its former colonies were located). And even if there were hostilities between the German Reich and the Soviet Union, it would at least occur through proxies as was the case in the Spanish Civil War.
To the best of my knowledge, the Reichskolonialbund was the foremost advocate of this endeavor. I am sure that, of the various factions in the NSDAP, they had the most to gain from German-Soviet rapprochement, especially if doing so means the realization of détente in Eastern Europe. After all, their downfall occurred unceremoniously in 1943, when the NSDAP decided their activities were not conducive to its strategic interests in Eastern Europe.
Now, what would be the intended outcome of that endeavor? It would still result in the Germans, Soviets, Italians, and Japanese carving much of the Eurasian landmass into their spheres of influence. Since the Germans will not be invading the Soviet Union, that will be happen, regardless of whether the US decides to intervene in the Second World War or not.
The Allies will lose most or all of their colonies in the process and there will be a subsequent Cold War, with the German Reich being the third power between the Americans and the Soviets. The Cold War will be multipolar as opposed to bipolar. And even if Imperial Japan and Fascist Italy managed to survive along with the German Reich, their presence only supports that conclusion.