UnitInstance and Allegience

Is it possible to use UnitInstance in a way to determine allegience of the spawned creatures?

Specifically, I want to make a spell (similar to Shadow World) that would create Goodie Hut that will in turn spawn creatures -> ok this is easy and it's what Shadow World does.

Now, I want to have those creatures join a specific faction when created. So, in essence the Goodie Hut would spawn creatures that are members of a specific faction.

Is that possible?

(Champions have this:   <RandomNPCAllegiance>Empire</RandomNPCAllegiance> so maybe something like this could be used here as well?)