NHF – new heroes for Heroes V 3.1.

I see this as redundant, since there is a Tavern.

Yes, but the respawn happens earlier, so it has an advantage. The hero will be ready for battle even before the next turn begins, and this could be one of the features.

You can farm an army on enemy roaches like this.

It's quite difficult to imagine this in the reality of online play.

This should be a large army
Maybe, let it be ghosts in a quantity equal to knowledge + spellpower * level.

No, it doesn't have to be large, the main thing is that there are seven units.