In the proposed variant, high-level units of another race are taken instead of one's own low-level units. However, this will decrease the morale of the entire army.

but morale is easily fixed with corresponding skills or artifacts...
by the way - I had neither leadership nor items like +2 to morale, but everything went very smoothly - no one put up a fight =) ...

Added after 1 minute

Does this depend on the game version? I have 1.0. I didn't find anything like that there.

you capture Apel-Sin, and throughout the entire game you buy twilight dragons there instead of your own dryads - that's all)
And as for the unbought dryads or dancers, of which several hundred will accumulate, it is very good to give them to Talanara and use them to crush side necros..