Hi, I think what you're looking for comes at Stage 7, that's when the Archer is introduced. And the Mage is introduced later. These units really change how the game is played and put a lot more focus on positioning than just weaknesses. Thank you for the in depth review :)
But yeah, how the theme fits is definitely a matter of perspective. For me, I made the game looking at the player as one unit, but they just change class every turn rather than several units in one.