Depending on numbers and training, this (vehicle mounted 20mm) could be another subtle and plausible upgrade to the Mobile Force.
I could see a tweak to the opening of the Battle of France, if there are sufficient numbers to have an impact. The Stukas, would become a bit more cautious in their attacks, so not as many sorties? If they are suffering painful losses, would the fighters get tasked with more strafing runs, to clear a path for the Stukas? Either way, the Luftwaffe effectiveness is diminished, but to what degree?
When the mobile 20mm's value becomes apparent, and war-time spending increases, could that weapon become a standard across the Army for local defense?