I have always loved the idea of having special variations of enemies, like the blue (champion) and yellow (rare) enemies in Diablo 3.
Give them more health, accuracy etc. But also give them special abilities from a list,
- Like being able to call in Juvies,
- harden themselves to make themselves take less damage,
- Dodge much more,
- spot the cog/fortifications
- focus swarm fire on one target.
- regenerate health.
- Heal other units
- Inspire other units to swarm/rush
You could give them a certain amount of abilities and increase the number with each difficulty.
