Hypothetical system. Why? Hadn't the chance before and it's better late than never. I know it's "too complex or whatever" but it's not like I'm know for designing good systems anyways. 
Any creature shares some basic stats and some combat stats. All of them work under the same ruleset. Creature Stats:
- Strength: bonus to close combat damage; bonus to weapon/shield wielding.
- Agility: determines Movement; bonus to dodge; bonus to Ranged Combat Attack; bonus to Initiative.
- Health: determines base Life; bonus to Nature resistance.
- Intelligence: bonus to Arcane power; bonus to Initiative.
- Willpower: determines initial Morale for battle; bonus to Arcane resistance.
- Charisma: bonus to Diplomacy.
- Sight: determines the range of sight of the creature.
The values of the different bonuses would depend of the value of the Stat, which is determined by the species of the creature. (Sovereign and Heroes can be different, normal creatures all have the same base values)
Channeler creatures would have Essence and Mana as stats too.
The combat stats are always the same and the values depend of the training of the creature. Combat stats:
- Close Combat Attack: value used in close combat.
- Close Combat Damage: value used in close combat for damage; based on weapon and strength.
- Ranged Combat Attack: value used in ranged combat.
- Ranged Combat Damage: value used in ranged combat for damage; based on weapon.
- Dodge: value used to dodge any kind of attack, paired against the attack values to determine if the attack is successfull or not.
- Defense: value based on the armour pieces used by the creature; in case of being hit, this value is substracted from the damage value of the attacker.
- Life: if it reaches 0, the creature dies.
- Nature Resistance: like Defense but only applies to damage of Nature origin, like poisons and acids or sicknesses.
- Arcane Resistance: like Defense but only applies to damage of Arcane origin, like Arcane Missiles.
- Initiative: how quick the unit react in battle.
- Movement: how fast the unit moves in the battlefield; based on Agility and affected by armour pieces of the creature.
- Morale: based on Willpower and any other modifier.
A unit need some training before it's ready.
- No Training: the unit gets no extra bonuses to determine que combat stats.
- Close Combat Training: bonus to Close Combat Attack, Dodge, Initiative and Morale.
- Ranged Combat Training: bonus to Ranged Combat Attack, Initiative and Morale.
- Scouting Training: bonus to Sight (altough it's not a combat stat), Initiative and Movement.
Except for the first option, the other types of training accept different levels of proficieny (Veteran, Expert...) and can be combined in different levels. Extra skills could be added to the training (if the unit is a Channeler, you could pick the spell for it to use).
Weapons and armours have strength requirements to be used. Same weapons/armours of different materials have different strength requirements to be equipped (mithril being lighter than iron or adamantium being heavier than iron).
