And regarding the creatures, I'm planning to rework the recruitment and building mechanics a bit.
Instead of having seven different creatures with two upgrades each, there will be four or five identical but independent creatures (let's call them recruits) with various development options (I've calculated about twenty-five combinations of armor/weapon for each creature). By building different types of structures in the city, such as armories or training halls, or by finding certain artifacts, you can improve the creatures in different ways, i.e., give them different weapons and equip them with different armor, which will determine their combat properties. So, essentially, the core of the army will be different versions of stormtroopers. One slot will be for a special "heroic" creature, meaning the hero participates in the battle; it would be strange in the Star Wars setting if, for example, Vader just stood on the sidelines. And one or two slots will be for an AT-ST walker or heavy equipment.