I think Frederick the Great built his reputation on manouvre and superb discipline. Perhaps there should be some rule to Frederick / the Prussians to use certain cards as the Le Grande Manouvre card, in the same way Recon 1 cand be used as Air Power in some Memoir '44 scenarios.
Perhaps also extend the "ignore 1 flag" to some Prussian Infantry units? And maybe Prussian Artillery can move 1 hex and fire like Horse Artilery?
Also, should Foot Artillery fire as Horse Artillery as they were lighter guns than the Napoleonic grand battery?
It would seem to me that if this project was to move ahead, the components are all there now.
My limited understanding of the 7YW forces is that as a standard, the Austrian army of the Napoleonic era was pretty similar to that of the 7YW era. The main exception would be cavalry, which was weaker and not a 'shock' arm. So perhaps reduce the cavalry strength to 3.
The main protagonists, the Prussians, are not as easy a match. I guess the Prussian army blocks would be used (though the French Blue might be better), but the cavalry probably needs strengthening to 4 blocks, and I'm not sure what enhancements the Prussian infantry should get, but should be superior to the Austrian infantry, in speed and firepower.
The French royal army performed rather woefully, and the Spanish army might be the model for them.
The Anglo-German armies are probably about the same as the Napoleonic era forces, with Portuguese substituting for the German allied forces.
Russian army, I have no idea.
However, I think getting the Austrian & Prussian forces right first will set the tone for the other armies.
Glory is fleeting, but obscurity is forever.