The main criterion is that everything must be appealing, useful, versatile, and accessible; there should be no silly, filler, or strictly situational perks, nor connections that confuse the acquisition of perks through other skills. Attractive magic transformations have already been prepared for Orcs instead of pathetic dampening effects, but let's take it one step at a time.
Offense: Hero's units deal 10/20/30% more damage in melee.
Tactics: The area for deploying the hero's troops increases by 1 row if the opponent does not have Tactics.
Speed Sorcery: The hero gains the "Area Haste" spell and the ability to cast it—at least at an advanced skill level—for 50% of a turn (+120% initiative in a 4x4 area for Spellpower/4 rounds for 16 mana). Barbarian/chieftain/shaman instead grant their troops a +1 bonus to initiative.
Battle Frenzy: The base damage of all the hero's troops increases by 1.
Archery: Hero's units deal 30% more damage when shooting.
Heroic Attack: The hero's attack deals 200% damage.
Stunning Attack: The hero's attack stuns the target (it loses up to 50% of its turn).
Witchy Attack: The hero's attack casts "Debility" on the target depending on the same Dark Magic skill (-8/10/12/14 to offense for Spellpower/2 rounds).
Tactics – Speed Sorcery
Tactics – Battle Frenzy
Archery
Heroic Attack – Stunning Attack
Heroic Attack – Witchy Attack
Defense: Hero's units take 10/20/30% less damage in melee.
Fortitude: The health of all the hero's creatures increases by 2.
Stone Hardness: The hero gains the "Area Stone Skin" spell and the ability to cast it—at least at an advanced skill level—for 50% of a turn (+12 defense in a 4x4 area for Spellpower/4 rounds for 8 mana). Barbarian/chieftain/shaman instead grant their troops a +10% health bonus.
Reflection: Hero's units take 20% less damage from Destruction magic spells.
Fireproof Armor: The hero gains +2 defense. Hero's units take 50% less damage from the Fire element and are immune to the "Fire Master" ability.
Evasion: Hero's units take 30% less damage from ranged attacks.
Deep Defense: When executing or maintaining the "Defense" order, hero's units receive an additional +25% defense (total +75%).
Readiness: When executing the "Defense" order, hero's units gain the right to a preemptive counterattack, ignoring even non-retaliating attacks.
Fortitude – Stone Hardness
Reflection – Fireproof Armor
Evasion – Deep Defense
Evasion – Readiness
Luck: The hero gains +1/2/3 to luck and offense.
Magic Resistance: Hero's units have a 15% chance to deflect enemy magical effects.
Ethereal Luck: Hero's units attempt to deflect enemy magical effects twice as often.
Soldier's Luck: Hero's units attempt to trigger random abilities twice as often.
Luck Stealer: The hero gains +1 luck. Enemy units receive -1 luck.
Critical Luck: Lucky attacks from the hero's units deal an additional +50% damage (total +100%).
Luck Energy: The hero gains +1 luck. There is a 50% chance that the hero's spells consume 0-50% less mana (random discount).
Sorcerous Luck: Hero's spells deal an additional +50% damage with a 10% probability for each unit of luck.
Magic Resistance – Ethereal Luck
Soldier's Luck – Luck Stealer – Critical Luck
Luck Energy – Sorcerous Luck
Leadership: Hero's units gain +1/2/3 morale. Reaper/cultist/Necromancer additionally give the enemy hero's units a -1/2/3 morale penalty (does not work against neutrals).
Troop Gathering: The size of the hero's units increases by 5% at the start of each day (rounded down).
Guild Master: The hero brings in 100 * (level + 2) gold at the start of each day. Enemy hero's troops receive a -2 morale penalty (does not work against neutrals).
Charisma: When attacking neutrals, before each battle, the hero has the opportunity to buy out 20% of creatures (rounded down) for 300% of the price.
Empathy: When positive/negative morale is triggered in an allied unit, the hero restores/loses 10% of a turn. Reaper/cultist/Necromancer additionally gain +1 spellpower for each level of Leadership.
Fight to the Last: Upon the death of any hero's unit, 1 creature with 1 health always survives if there were several creatures in the unit before its death.
Inspiration: The hero gains the "Inspiration" ability (restore 30% of an allied unit's turn).
Retribution: Hero's units deal 5% more damage for each positive point of morale. Reaper/cultist/Necromancer additionally gain +1 offense for each level of Leadership.
Troop Gathering – Guild Master
Charisma – Empathy
Charisma – Fight to the Last
Inspiration – Retribution
Logistics: The hero's land movement distance increases by 10/20/30% (base 40 units).
Path of War: After each battle, the hero restores 4 turn points.
Looting: The hero does not spend turn points to collect resources, enter buildings, or board a ship. Enemy hero's troops receive a -1 speed penalty (does not work against neutrals).
Reconnaissance: The hero's vision radius increases by 50% (base 20 units). The hero can see the exact number of creatures in other armies if they do not have Cloaking.
Cloaking: The hero's vision radius increases by an additional 100% (base 20 units). The composition of the hero's army, except for the strongest unit, is hidden from the opponent if they do not have Reconnaissance. Enemy hero's troops receive a -1 initiative penalty (does not work against neutrals).
Unraveling Secrets: The hero gains the ability to learn spells used by any units or the enemy hero in battle, and also sees the enemy hero's inventory and spellbook during combat. Barbarian, chieftain, and shaman instead grant their troops a +1 bonus to initiative.
Pathfinding: The penalty for the hero crossing rough terrain is reduced by 50%.
Speed Aura: Hero's units gain +1 speed.
Path of War – Looting
Reconnaissance – Cloaking
Reconnaissance – Unraveling Secrets
Pathfinding – Speed Aura
Engineering: The hero's war machines gain +5/10/15 defense and offense, and +100/200/300% durability. Tent healing is increased from 10 to 20/50/100. The supply train increases the offense of shooters in the hero's army by 1/2/3. The catapult hits a designated target with a probability of 30/40/40%.
Ballistics: An allied ballista (if present) fires 2 times per turn, is controlled by the player, and is restored after battle.
Rate of Fire: An allied ballista (if present) fires 3 times per turn.
Military Medicine: An allied tent (if present) gains the ability to resurrect creatures, is controlled by the player, and is restored after battle.
Plague Tent: An allied tent (if present) gains the ability to shoot at living creatures.
War Craft: The hero's war machines gain +3 initiative.
Artillery: Before each battle, 10% of enemy troops die (rounded down). During a siege, an allied catapult fires 2 times per turn and is controlled by the player. The supply train is restored after battle.
Sulphur Rain: Before each battle, a total of 20% of enemy troops die (rounded down). During a siege, an allied catapult fires 3 times per turn.
Fire Arrows: An allied ballista (if present) ignores 50% of the target's defense when shooting, deals an additional +50 fire damage, and is restored after battle.
Ballistics – Rate of Fire
Military Medicine – Plague Tent
Military Medicine – War Craft
Artillery – Sulphur Rain – Fire Arrows