The problem with this alliance is the reason it failed historically:
Poland's stance on the issue ultimately determines how acceptable this is to France, because while the French might be willing to let Soviet influence expand westward, they wouldn't be willing to force the issue if Poland flatly refused to let Soviet troops into their country.
Aka, if Poland says no (like they did historically), then the Soviets would have to invade. That means France is supporting a Soviet offensive war against Poland. While the Poles might not want to join an alliance with Germany under normal circumstances, they might be willing to let German troops into the country when they end up at war with the USSR and have no allies anywhere else to turn to (while Britain wouldn't back the Soviets, they definitely wouldn't oppose the French either, and likely would just sit the whole thing out).
Remember when it comes to Hitler (who speaks of people more readily believing a "big lie" than a small one) and the Poles, that he had this to say in public circumstances (in
1938):
“The most difficult problem that confronted me was that of our relations with Poland. There was a danger that Poles and Germans would regard each other as hereditary enemies. I wanted to prevent this. I know well enough that I should not have been successful if Poland had had a democratic constitution. For these democracies which indulge in phrases about peace are often the most bloodthirsty agitators for war.
In Poland, there ruled no democracy, just a man. And with him I succeeded, in precisely 12 months, in coming to an agreement which, for ten years in the first instance, entirely removed the danger of a conflict. We are all convinced that this agreement will bring lasting pacification. We realise that here are two peoples which must live together and neither of which can do away with the other. A people of 33 million will always strive for an outlet to the sea.
A way for understanding, then, had to be found. It has been found and it will be even further extended. Certainly, things were hard in this area. The nationalities and small national groups frequently quarrelled among themselves. But the main fact is that the two governments, and all reasonable and clear-sighted persons among the two peoples and in the two countries, possess the firm will and determination to improve their relations.
It was a real work of peace, of more worth than all the chattering in the League of Nations Palace at Geneva.”
Recall that Hitler was a professional liar, and he'd already signed a nonaggression pact with Poland in 1935 (and stated clearly that he had no intent to annex Austria, or to take further conquests after the Sudetenland). He would subsequently sign a nonaggression pact that included a lot more than just noninterference between the Soviet Union and Germany (including arms sales of substantial naval equipment, i.e. the heavy cruiser Lützow and a dozen 15-inch guns for the Kronshtadt battlecruisers, as well as blueprints for the Hipper and Bismarck). German forces even abandoned captured territory in Lwow to the USSR in exchange for securing control over oil fields in Lublin (the borders of Poland were not exactly set in stone with the original treaty, and moved around once the two powers occupied Poland).
So the real question goes back to Poland, who on the one hand was unwilling to let Soviet troops into the country; if they won't let German troops either, then the country just gets steamrolled, with Germany likely not attacking at all and just using it as a propaganda tool against the Allies.
