If Stalin was hoping to avoid the 1939 scenario then he shouldn't have agreed to the MR pact, plain and simple.
Are westerners organically unable to think for a couple of minutes as state leaders, they blame? I know that you are always saint, even when commit a genocide, but that is some really high level of hypocrisy.
We are Stalin. Leader of only socialist state on the Earth, and having lot's of problems because of it: both "democrats" and "fascists" don't like us much. Germany is rebuilding it's might, openly violating Versailles treaty, and noone cares. Maybe because program of nazi regime is built around claiming land on the East. Our land up to the Urals.
We help to the lawful government in Spain in it's civil war agains fascist rebels. "Neutrality" of France and Britain leaves free hands for Germany and Italy. Civil war is won by fascists. Great!
Germany literally annexes Austria. Noone cares.
We suggest collective security pacts to Britain and France. Each time, we do this, they find plenty of reasons not to sign such treaty. We succeed to sign a security pact between us, France and Czechoslovakia. Good. As soon as Germany starts claiming Czech land, France declares that it is not their problem, literally violating the pact. We declare that France can go and f*ck itself - we are ready to help to Czechoslovakia anyway. Poland refuses to provide us a military pass for fully legitimate help. Maybe because they also have plans to steal some Czech land with some industrial objects. Czechoslovakia is fed to Germany and a bit to Poland. France and Britain are happy - they manage to avoid war, letting Germany to move East.
Summer 1939. It is obvious that Germany will continue it's game of annexations. We again suggest to France and Britain collective security pact. They agree to negotiate but send men who are not authorized to sign anything. Great!
And at this time German Foreign Secretary arrives. He suggests us the treaty to define spheres of influence in Eastern Europe and non-agression pact. Germans for sure will violate it earlier or later, but still, we can win some time with it. While Germany will be busy with France and Britain for some years, we will rebuild our army, rearm it, prepare mobilization plans.
Will you refuse such offer even if it comes from pretty aggressive Germany?