First, it's important for me to thank all the modders that contributed to this great experience. I played High elves on the table top, so this mod is great chance for me to see warhammer armies marching in one of my favorite video game engines.
I've spent some time playing as Caledor, Naggarythe, and Avelorn, but my most advanced campaign has been with Saphery. I've also played around with the sample armies in custom battles.
I think you've done a great job with the various units of the table top game. The unit balance seems pretty good, but it's a beta, so I have a few suggestions.
cavalry units are a bit too few in number. At my current settings, spearmen come in units of 160, and cavalry in units of 40. They do the damage I expect from a unit of charging cavalry, but they take a few casualties and don't have the numbers to keep going. I would suggest increasing their base number to 50 or 60
The mages of Saphery are very fun to use. I like the effects of their attacks, but I think the apprentice mages of saphery are too strong. They are widely available, for a cost comparable to a unit of bolt throwers, but they are far more effective on the battlefield. My suggestion is that their attacks should be less accurate. Currently, they rarely miss, and that allows a single unit of them to quickly kill an entire enemy unit. If they were less accurate, they wouldn't be quite so devastating.
Next, I am confused by how temples work. Sometimes I have the option of building more than one type of temple, but they seem to cancel out the effects of previously built temples. Were they meant to be exclusive? Are there suppose to be more religion factions than cult of pleasure and worship of Asuryan?
Finally, I have some suggestions for the planned "Struggle for the old World" factions.
I think it would be interesting if the various factions had very different build trees and economies.
Empire and Brettonia can have traditional economies with plenty of ported over buildings. They are the base after all.
Dwarves should have slower population growth, (can there be a faction wide penalty, just behind the scenes?) and to make up for it, they should get bonuses to mining. They should get general traits that give + to mining, as well as anciliaries, and they could even get a more advanced mining building that only they can build.
Orcs and goblins should could not have access to the higher markets, but should get lots of bonuses for looting. plenty of traits and anciliaries to increase income from looting.
Tomb Kings shouldn't do trade at all. I'm not sure how feasible it is, but if they couldn't build markets and their ports and roads didn't give any bonus to trade, that would be good. Instead, they should get bonuses to taxes to make up for it. Of my ideas, I think this is the most difficult to implement, so I'll understand if you go with something less radical, but I think not trading reflects their lore.