New light barracks to compliment the dark barracks. Troops could consist of natural creatures like wolves and nymphs. New resource collectors could be created and storages for the material needed to create these troops. Maybe players could only choose the dark or light path as a little spin on it.

New dark barracks troops:
Inferno warrior- wields the power of an inferno tower, possibly holding one on his back or in his hands, slow moving, not too tanky, but can attack multiple structures at once. It would need to be expensive too.
Necromancer- similar to the witch, can revive fallen troops for either a certain amount of time or with a fraction of their health. This could either be a new troops or a power of the witch when she is upgraded to higher levels.

Spell:
Zombie spell- similar to the necromancer idea, the zombie spell would revive fallen troops but only for a certain amount of time. It would need to be the last spell and expensive as I could see this becoming overpowered.

That is all! Thanks for reading!