An idea is that your channeler can make certain items for your units like say make a unit who could cast a fire spell with a magic ring of fire. For instance he could cast a fireball that lets him act like artillery or imbue his sword with fire to make him stronger.
Now the fallen are described already so the tech is there to make some units like them say by imbueing part of a cyrstal shard in there skin making them stronger faster and more resliant.
Already in. Not those particular items, but the general idea is there.
Also on a side note there should be elves
There will not be elves in the vanilla game. This will aboslutely not change. However, elves, orcs, faeries, and pretty much anything else you can think of will be modded in almost immediately.