several advice

simple version:

1) game speed: Instead of an year per turn same in all speed mode, season per turn or month per turn felt much more comfortable and reasonable to look at, especially for the player who always choose endless.  

2) Special units: set an numerical limitation for Special units, remove generalized "special" unit as such as "red coat" which is essentially British style regular line infantry, add specific unit such as Cold stream Guards or The Old Guard/La Maison du Roy etc.

3)Tech tree: Expand and rework tech tree, Instead of compile all tech in one Era, divide era into three time period (early, high, late) so player could enjoy these technology before hopping to next era.

4)Sephere of infulence: add more benefits for sephere of infulence, my idea is that The independent Nation should produce their army units (the units player is going to hire) according to sphere of influence. 

eg: if “German” owns more than 50% influence over the region, the independent nation will produce German special units mixed with General units. 

5) officially add more culture form different era, modes can be annoy when player didn't remember which one he turns off last time.

6)Most importantly, Line infantry tactics or Line of battle is definatly not an Industrial age tech!!! return it to early modern age, pleace. 

Napoleonic warfare/Levée en masse is much more of an logical name for adding an unit slot than field hospital. Let doctors and nurse do their job by rescue the wounded instead of producing more of them.

7)Not all field guns are howitzers, it is like light cav heavy cav, light infantry line infantry/heavy infantry, modern artilery may not have difference but back in 1700s, they do.

8)Pleace further improve diplomatic actions, add territory trade or liberate ally cities, or at lease allowing player to give direct monetary relief to other states. I understand that trading territory may conflict the idea of nationalism, but I don't want to held lost territory for my ally becase they couldn't defend them properly.