Heroes 5.5 WarGame Edition - Tactical Edition.

If there's a Paladin, I don't understand why there also needs to be a Knight. In terms of meaning, it's like creating "Knight" and "Honored Knight" as separate classes, with both being alternative options.
Not to mention that this simplifies the process of choosing unit names (it's easier to come up with a name for human cavalry so that it doesn't overlap with the hero class name. Otherwise, we have a Paladin class and a Knight class, and there are almost no names left for the cavalry... Well, if the goal is to eliminate duplicates, this is what we should do).

The image of a Paladin differs from that of a classic Knight, just as a Witch differs from a housewife with a broom.
A Paladin is a Knight with serious magical abilities. A regular Knight is not associated with magic in any way.

As for the duplication of unit names, this is too strict a requirement. If we follow it, many classes/units will lose a significant portion of their charisma. At least, I can't come up with such names. Knight, Paladin, Druid, Priest, Fiend, Assassin, Reaper, Warlord, Shaman.

Added 4 minutes later

Then we have two options.
1) There's nothing to remove the buffs with. Okay, then why do we need another school of magic? We've already gained a significant advantage. Combat skills will only strengthen him.
2) There is something to remove the buffs with. Okay, we repeat our debuffs to maintain the army's combat effectiveness. Why another school of magic?

1) It's not necessarily an advantage; I listed slowing/weakening/strengthening debuffs for a reason. Their role is to buy time for the hero by reducing the enemy's damage by a significant amount, not to kill them with troops.
2) It's not necessary to repeat them; you can play with the ones that remain. They give you armor - okay. They give you a curse - counter it with a blessing. They give you a slow - it goes without a counter. We move on to the next stage, to the killing spells. If we only play with debuffs, a 3rd school is definitely not needed.

An area-of-effect Stone Skin reduces the damage received by 2-2.5 times. An area-of-effect slow reduces the enemy's initiative to 30-40%. If both of these debuffs are active, no combat skills will be needed for the Archmage to survive.