Auto-translated
I think it's perfectly fine to mix troops from different factions in your army, as it lowers morale, and, they say, troops from a different faction that are in the minority will desert. So, if you're not afraid to lower the morale of your troops, you can add even undead, which have an unconditional advantage – transforming other races into their own kind. 8) An uncapturable city is nonsense; no matter how many times I've played Disciples, I couldn't understand WHY??? It's so satisfying to capture an enemy city, their stronghold. 8) It's just a pity that you can't destroy it or loot it. IMHO, the most sensible city capture system was in Age of Wonders – there you could loot a captured city for several days, destroy it, or drive out the local population and populate the city with your own race.
ГРРРРРРРРРРРРРРРРРРРРРРРРРР!