Was going to post this on steam but this is probably a better place for it, where all the experienced players are who may be most resistant to change! Has the idea of magic cards been discussed already? I feel like a lot of units could be re-designed and replaced by magic cards, there could be a lot of ways to implement them but i think the Zombies would need their own form of magic cards to compete.
Alternatively, each faction city could have its own basic upgrades that could also fill in for what some cards already do. They’d cost gold or mana or population depending on the race. You could only do one upgrade in a city and have a few good options like increased training time, bonus defenses, more gold income, added mana income, the ability to deploy trained troops a league away, train troops with combat experience, add a second training que and more.
Personally i really like the co-op aspect of the game, bringing and offering cards that your allies can sometimes use, and i think thats where Magic Cards could shine. With every race bringing their own small selection that can be shared with allies or used on them without them having to own a city of your faction. Or just having all the players cards pooled together globally and drawn from as needed, so you may just bring cards that mostly benefit allies situations.
Adding new units could fill all the roles of magic cards but you run into deployment issues when using a unit just for a spell.
Then giving zombies their own tricks could make them more unpredictable than ever. I had the thought that whenever they take a capital city, they spawn and use a card somewhere. There will be a warning indicator that will show you what the card is and where the effect will take place.