Some fun twists and mechanic reworks that polarize strengths of each race.

Race Enhancements-

Dwarf: default army away time cut to 18, after transport it cuts to 12 hours. MP gate is not available
Elf: no retals given for offensive spells, potency of spells capped at X schools per land.
Orc: 3TC and 2 ATC units trained per castle
Gnome: Homes house 25% more peasants and reproduction rate is 30% faster. Markets are 20% less effective.
Human: Mounted Archer becomes TC unit, pikeman becomes ATC and requires plate armor with minimal or no statistical changes.
Undead: 10% of killed units return as fodder unit

World Building:

Thievery: Schools can train wizards or thieves. Each race has a baseline for thievery just like they do magic.

Orc- -25%
Elves -15%
Human- 0%
Undead 5%
Gnome +10%
Dwarf +20%

Thieves can be sent on missions. Higher number of thieves sent means better results, but also increased chances of being caught (killed) and percentage chance of completing assigned mission against their own kingdom in trade for their lives.

Gold heist: Steals % of gold
Wood heist: "
Iron heist: "
Food Heist: "

a) Poison: poison enemy food stores resulting in % of food stores being destroyed
b) Assassin: kills small % of troops in their sleep (results in death of thieves)
c) infiltration: gather details on enemy kingdom- Armory, technologies, units training (more info divulged with upgraded thievery techs)

New Races:
Dark Elf
Giants
Hobbit
Centaur