Long ago in the good ol' times of 2015, a thread was posted in this very forum with a similar name.
I was thinking about the idea of some sort of officers before coming across this, but I understand the issue inherent with his idea and I think I know how that can be remedied.
In the militaries there are already "generals" or "admirals" that lead the ground, air, and naval forces. What if they had improvable stats like baseball players?
So, let's say, Admiral Whatshisface is the admiral of a just created nation. He spawns with any age between 30-40 and will automatically retire when he is 65 and be replaced by another admiral aged 30-40. For the Navy the stats would be naval based. For ground as well, and likewise with air. Whatshisface's stats would directly effect the nation's naval capability and give a bonus to combat rolls.
That is the base of what I'm proposing [EDITOR'S NOTE, it is a shitty idea and I retract my support of it after further thought. Everything after this point is more interesting!], but I think an element of strategy more than just pouring money into your officers could be available. Like, perhaps, a trait.
Say a nation wants to raid with the Navy, then the player could choose "Coastal Raider" (Allows loot gain from naval attack, -10% defense) for their admiral. Or if they want a defensive Navy, then the player could choose "Defensive" (+10% to defense, -10% to offense) for their admiral. Or, au contraire, "Offensive" (+10% to offense, -10% to defense). Or maybe "Balanced" (No effect). Or some production changes like "Quality" (+50% unit cost, +15% overall) or "Quantity" (+1 off-map dockyard per 3 cities, -50% unit cost, -30% overall) et cetera. How these would work would be like current War Policy or Domestic Policy but 1. you can only change it once every [insert large amount of turns here] and it will cost exponentially more every time you do it to the same admiral. When the admiral retires, you get a new one for whom you can pick a new trait.
Personally I prefer this ^ to having a system like baseball, because it's kinda boring to just press a button upgrading someone over and over again. But maybe a combination would work?
I am 110% open to criticism and suggestions, I'll edit this post as more come in.
More detailed ideas for other officers:
Notes and clarification:
Percent bonus applies to everything in combat including infrastructure, money, planes etc.