NHF – new heroes for Heroes V 3.1.

Greed:
The more gold, the greater the bonus.
The bonus could be defense, for example. Dwarves really love mining and then guarding gold.
If not defense, then at least mana or creatures.
Mage Killer:
The more spellcasting units killed, the more casters join the hero's army. Increase in druids (creature level * number of slain creatures / 100)
Ranged Unit Killer:
A bonus to attack is given for each ranged unit killed.
Hunter
Places traps on the map with debuffs.

Before a battle, the hero destroys as many enemy creatures as there are "ranged" units in the hero's army, depending on the ratio coefficient between the creatures.

There's an idea to create a Hero-Heaven character who revives Necropolis creatures back to life according to the undead raising table.

In treasure chests, the hero finds more gold, artifacts, etc.

Academy:
the hero receives +1 to knowledge from the start of the game and +1 for every 3 levels; the bonus works if the hero was in the Academy town no later than 2 days ago.

It could be possible for a mage to sell artifacts directly on the battlefield.
For the League, each artifact purchased in the city provides a permanent bonus. Here, selling each artifact could give the hero a bonus.

I would combine these two specializations here:
The hero gains a level up for each mastered school.

A dwarf receives a defense bonus depending on how many mines he has, but not exceeding the hero's level.

There is an idea for a hero who receives a daily bonus according to Sanctuary (there, depending on what day of the week it is - that's the bonus). Fagus, but not random, essentially))

Well, I will offer my own specialization idea: "Charm" - based on Heroes IV!
So, the hero (but preferably a heroine) possesses the gift of charming creatures of his/her native race, but it needs to be fueled by mana to increase the charm level!
To make this spec passive, I see the following way... at the end of the week, the hero's mana reserve will reset, but at the same time, the charm will increase, i.e., the charm level, from which the % probability that neutral creatures of the native race will join the hero in a certain % of the squad size will grow; this % will increase with the hero's level!

Increase in knowledge or attack per level.

Several ideas for dwarf specializations:
1) All water, air and earth elementals entering the hero's army become fire elementals. Also, after battle, for each tier-7 dwarf unit killed, the hero receives +1 fire elemental for every 6 levels of the hero. (Brief outline for bio: specializes in fire elemental energy. The hero converts elemental energy of other elements into fire energy, also uses the released energy after dragon deaths to summon elementals).
2) The hero can move between captured mines (in terms of underground tunnels), losing all his movement points, with distance increasing with level.
4) Each time he gains a level, the hero reveals a relic or major artifact on the map. When picking up an artifact, the hero replenishes mana and movement points.
This is what came to mind first; I might think more later, maybe come up with something better and less forced.

How about an idea for a hero who, depending on his/her level, can reduce the effectiveness of enemy artifacts (all possible ones or just one parameter)?

Idea for a specialization for some male hero: "Womanizer".
The essence: The hero receives +1 to defense and attack for every 50 beasts / furies / harpies or every 8 witches / shadow lords / mistresses, 25 shamans / daughters of earth / daughters of heaven. If he loses his own girls, including those in battle, the skill decreases by twice as much and minus one to morale. The overall increase (decrease) increases by 1 unit of defense for every 9 levels of the hero. But that's not all. For having under command sympathetic heroines from the League of Shadows, Forest Union and Order faction, the hero receives 10% to the total skills bonus per heroine. Nuance: if the heroines die, the hero loses the bonus threefold. If there is Vidomina on the map, the hero's morale is constantly equal to minus three plus one for every 7 levels of the latter. That's how it works. A well-thought-out spec with great originality.