I would just want to see more units really
France:
-Chasseurs a Cheval
-Moar Germans (Westphalians, Saxons, etc.)
UK:
-Scott's Greys
-28th Foot
-KGL light foot
Prussia:
-Fusiliers
-Real uhlans, not those landwehr pretenders
Russia:
-More variation for the line infantry >.>
-Finnish units
-Variation in the cossacks, I don't think the blue pajamas would have been universal for irregular cossack troops
Austria:
-More German infantry
-Landwehr units
-Czech troops
-Maybe another grenzer unit