I've been playing recently and I as much as I love it, I have some suggestions.
I think you should make lifeguard pikemen the default pikemen for sweden. They have spectacular colors and just look great. The colors of Sweden. Mind you I know by this point the colors of Gustavus Adolphus, the yellow with blue, were not exactly the mid century fashion or how the army looked. I'm suggesting that the lifeguard pikemen become Swedish pikemen instead and form more of a core of their army. I'd love to see an unarmored version of them as well as armored.
I would love to see the German pikemen with baggy pants restored as mercenaries somehow. Baggy pants still did not entirely go out of fashion at this point, though hongrelines and justacorps were generally replacing them, especially in armies.
I'd love to see some more outfits or special outfits used for mercenary halberdiers. The cloth they wear makes sense, but in a way a lot of said outfit repeats on a lot of troops. It looks a little bit bland. You could restore the old German pikemen (and musketeers) as mercenaries and give them the baggy look, for example.
I think Scots should also be available as mercenaries in taverns.
I would also like to point out that there is something in your mod that has affected the weather system, and compared to vanilla or HoH that I also played alongside your mod, there is a lot of beautiful weather and lightning specific to WFAS that somehow just got removed. I could show you screenshots of what I mean. I'm a little lazy to upload them right now.
Now I'm not sure if there's anything you could do about this, but I finished the black mace quest and I'm the permanent marshal of cossacks hetmanate. Factions seldom declare war and the AI for the most part refuses large engagements. Everything is very slow, as are the declarations of war. Lords seldom offer a "provoke war" quest with a kingdom, and I'm barely seeing nations marshal their armies. The commonwealth is exhausted from the war on all sides and it musters very little troops per each lord, meanwhile the cossacks have grown "fat". The lords don't exactly know how to engage in field battles even if they could join in and turn the tide of battle, they would rather run away. They only usually ever engage if the tide greatly favors one army over another. Autoresolve greatly favors the defenders no matter how large of a cossack army I have behind myself (and boy, is it large) and its difficult to win more than one fortress that way. I have to go around conquering fortresses personally, which, to be frank, due to the AI issues and everything, in the cases of most forts, is rather boring in this game. Especially when the odds are so unequal and clearly favor the attackers. I think the autoresolve is something to be looked at.
I do not remember if I ever had large battles (300 men per side engaging) unless I had intervened and caught the AI while the friendly and enemy AI was in my zone of influence. Usually, two marshalled armies will not engage each other fully. One lord will get ganged up on, some will join in, and the rest will scatter and flee. This is probably outside of your control but its tiresome when all I want to do is have big, decisive battles. A lot of the factions are passive a lot of the time and they seldom marshal armies after a while.
Also, the food tends to run out way too quickly lategame with 130 soldiers. It instantly leads to disease and troops dying, and its usually not sold (at least not in desirable quantities) outside of villages. It isn't really a feature at this point, just an annoyance. I think you should increase the size of the foods in stock, or decrease the amount the armies consume. I also think fiefs, even a single village, give way, way too much gold. Once a player gets a single fief he can bathe in gold.
That's it for now, I think. Enjoying your mod greatly, but I realized that after completing the main quest (with few memorable battles to show for it) i am discouraged from continuing on because of the aforementioned issues. I got to that point yet I haven't enjoyed many decisive, large battles.
EDIT: I'd also like to say that its far easier to resolve rebellions and persuade lords than in vanilla, even with low persuasion. I think this is something to be looked at as well. If you could add some better renown gains for certain quests that would be nice too. Since one cannot become a mercenary, grinding renown to 200 can be a bit of a chore.
And happy ten years, Csatadi mod! You are awesome!