Hitler knew the Poles would never go for that.
Ironically, one of the men Hitler most admired was Marshall Pilsudski. Even attended his funeral. And when the Nazis invaded in 1939, he had them send a guard detail to guard Pilsudski's tomb. In the early days, Hitler envisioned perhaps having Pilsudski as an ally against the Soviets, knowing full well of Pilsudski's hatred for all things Russian. Although by all accounts of the man, it would have been hard to imagine Pilsudski agreeing to be partners with Hitler.
One reason the Nazis opposed the Poles so much, was because of their racial theories, they surmised that since many Poles had at least some Germanic blood in them, that they would be a formidable foe, and therefore, unlike the other Slavs, that they considered untermenschen and didn't stand as much of a threat, the Germans genuinely saw the Poles as an enemy that had to be wiped out, or else they would always pose a threat to the Reich. It also explains why the Germans never allowed Poles to work as guards at the Death Camps....give a Pole a rifle, and the first thing they'll do with it is shoot the German.
I went ahead and deliberately violated henkster’s Law of Alternate History; the alternate history isn’t valid if it involves Hitler not being Hitler and the Germans not being tne Germans. My scenario certainly had Hitler not being Hitler. Whether or not the Poles would have gone for the gambit is irrelevant; to Hitler it was unthinkable.
The Poles were not in an enviable position. They were in the process of exchanging one oppressive occupying alien regime for another. Regardless of whether or not the Warsaw Underground rose up against the Nazis; regardless of the outcome of that uprising, that exchange was going to take place. Poland’s fate was sealed as early as Munich, but certainly no later than Stalingrad.