I have a idea for the squad leaders (just types) :
in mythology, there are several types of creatures that have legends or great stories in several types of troops :
Soldier <- is almost filled by human
Archer <- Elf
Heavy <- Dwarf
Pikemen <- Human / Half-human(fast running animal) / Goblin (maybe develop can make story for goblin)
Cavalry <- Centaur
Mage <- pure blood Demon (maybe develop can make spesial story for a pure blood demon that live with human)
Healer <- Angel