Heroes 5.5 WarGame Edition - Tactical Edition.

Well, for now, there are vacant skills – Barbarian Light, Darkness, Chaos, and Summoning debuffs.

More. For example, there are unusable perks (e.g., Archer Enhancement). Or a perk where the entire effect is simply giving an active skill (Vigil, Reinforcements). These can be given as a spell, and the perk itself can be used for other purposes. From these, you can easily create a skill whose effect will be achieved through scripts and/or buffs.

The debuff effect itself definitely won't be there (there are specialized perks for this – corruption, hold, weakness – 3 perks are definitely enough to bring down any school).
But what will happen is a question (for now, just stats are suggested).

Just stats are very boring.

There is also the Barbarian education skill available (Barbarians currently do not have access to it), the effect of which can theoretically be completely blocked and rewritten.

Is this the one that glitches with the Mentor and doesn't reset stats? :D

The only requirement is that the skill must definitely play a role in combat, like the new logistics (which will additionally give a starting bonus of 0.1/0.2/0.3 ATB to creatures – and this bonus is especially strong for low-initiative creatures, like undead).

Em... I'll divide it into 2 parts:
1. Are the additional bonuses of a "strategic" skill (+units, +money for units) considered to be "playing a role in combat"? For example, like the racial bonus of the Order faction (in the part that deals with retraining) – is it considered?
2. Logistics +10/+20/+30 is very, very, very strong. This is, like, Wingael at level 30, who is cut and banned in all sorts of mods.

At one time, I liked the role-playing model from Heroes 4 (compared to Heroes 3). You can consider options from there:

I also really liked it and still do. The advanced class system is very interesting.
Not throughout the text, but only for the critical (for me) points:

4. Leadership: increases luck and morale. There are analogs – Leadership and Luck. In Heroes 4, there is defensive luck (to reduce damage), and there is also an analog of this (unlucky).

Here, I was always annoyed by the unfairness. The basic Luck skill, for which the hero spends a skill point, gives banal +1 to Luck, which is perfectly replaced by a minor four-leaf clover in effect. The same goes for Leadership. I would add additional bonuses, taking into account the possibility of using combat scripts.

5-8. Combat, Melee, Ranged, Resistances – useless, as the hero is not a unit. But there are analogs to increase the hero's damage (in the Attack branch, double damage and stunning strike).

I disagree. Yes, the hero is not a unit, but can actively participate in the battle with his attacks. There are many options here – shift forward in ATB after using a simple attack, give a chance for an automatic second attack on the same target, increase the hero's level with a direct attack (if possible), improved Vigil/Bane/Reinforcements.

13. Nobility: increases growth in the city. For this, you need to tie the hero to the city, I don't know if this is necessary. There is an indirect analog – troop gathering, +10% to the number of each unit daily (rounded down). Naturally, also add restrictions on the hero's level, for example, the total cost of such bonus units cannot exceed 100-200 gold for each hero level.

As in MMH5.5, this is implemented through the governor's scripts. Why not? A little lower – more details.

14-15. Economics and Mines. Just money and resources. I don't know if this is necessary. But as an additional effect, resources can be tied to the racial bonus of the Dwarves.

Is it necessary? Yes. This is variability. Either you dump all the experience from neutrals on one hero. You get, say, level N and a good hero-killer. Or you spend experience on a hero-killer and on a support hero who will bring additional units and additional money for these additional units. As a result, the hero-killer will be M levels lower, but with an additional army. Who will win? Quality or quantity? This is like leveling up.

35. Summoning: summons certain creatures to the army. It is intended to have analogs for the Orcs (wolves, manticores).

A strange choice for the Orcs – wolves and manticores. Melee units without access to Blood Rage.
L = Logic. And a little NCF.
League. We learn Summoning. We summon Medusas. Ranged unit. If we want to go into ranged units.
Alliance. We summon Pegasi (a very beautiful unit). If we need mid-level flying units.
Necropolis. We summon RS (I missed them so much). A heavy, accelerating stack. As a variation – with Vampirism.

MMH5.5 – pioneers in terms of classes, I'm not sure that without such an example, I would have been able to do better on the first try. Therefore, criticizing their version, I am glad that it exists and allows you to see how you can do better, without repeating their mistakes.

Yes. I would set up a dialogue with the creators of MMH5.5 so that the truth would be born in the dispute.

By the way, I played one game (War and Magic), where 95% of losses are restored after each battle, a very interesting idea. ...

Here are my thoughts on this. Leveling losses in a battle = leveling "grinders" and "players".
Let me explain.
Initially, I played Heroes 5 as a "player". I didn't know many tricks, I just played. But then I switched. I found "tricks", "abuses" and just bugs. I honestly reported the bugs, but what can you do about "abuses"? If the game mechanics, without a bug, allows you to use the fact that a fake kills a hundred zombies? A newbie doesn't know this. But I already know that with one Hunter, I can even kill a hundred slow units – initiative and speed allow it. This is game experience. Don't deprive us of this.

What I want for PvE battles is tension. There is a way to give variations to each neutral stack in terms of types (melee + ranged + casters) and a hero. (this is needed for some curses for them, but it will not be possible to fight neutrals without consequences)

What consequences can this have:

Harsh, but my brain theoretically cannot calculate this yet (my higher mathematics teacher would now say that I am lying, but this is not so – with age, I have spent my operational part of my brain). Need to think. I can hardly even perceive such things as "expected value from Luck +5". I simply accept it as +"50% to damage over time" (in the classic version, of course). Valery Ivanovich tried to hammer his theory of probability into my brain. And in general, 60% of the brain is just fat.