Grinding it down
I think the only thing this would do is force the Germans to slowly grind the Polish Army instead of rapidly tear it apart. I have doubts that a doctrine would be in place to properly deploy the anti-panzer firepower in such a way to negate the armored spearheads. Encircled and flanked forces still have to retreat and withdraw and the basic/primary actions of the campaign remain. I suppose implications on the other warring powers and German speed in France or the Soviet Union is more open to debate.
The Germans could grind it down--but the casualty count would be much higher, possibly. I'm not expecting a Polish win. But, everyone would know that tanks have thinner armor on the sides than on the front, so there would be plans to take them from the flanks. Germany could end up with many fewer tans, and fewer tank crews.
If Germany was getting chewed up, would the USSR honor its treaty comitments to Germany, or would Stalin grin as German panzers burst into flames? USSR not invading Poland would be a massive change. (So would the USSR getting some of its tanks shredded.)
If Stalin was on the edge of going or not going, he might pressure Poland to provide samples of their wonderful tank killer, and manufacturing specs, in exchange for peace.
Hmmmm...Red Army gets Bazookas/Panzerfausts, and starts issueing them widely. Might that end up causing Germany to reconsider Barbaroas?