I'm a big fan of spirits so I've been working on guidelines for them, as I feel the structure of Genesys works perfectly for them without me having to do a whole lot.
To cover the broadest range of nature spirits, I figure 6 primary domains cover most things. Water, Earth, Sky, Fire, Animals, Plants.
River, lake, sea, ocean spirits are Water.
Soil, rock, gem, mountain spirits are Earth.
Wind, cloud, lightning, rain spirits are Sky.
Animals covers all living (non-humanoid) creatures.
Plants covers all vegetation, including mushrooms (Personally I have an additional category for Fungus but for most games it's a bit silly to separate fungi from plants).
Example:
Plants skill are granted Attack, Barrier, Conjure, Curse, Heal, and Utility.
Attack - Ice option just turns into "Entangling vines"
Conjure only creates plant matter, or summons barely sentient plant life.
If you want a Great Lighting Hawk spirit, just make a spirit with the skills Animal and Sky.
I toyed originally with just having a Spirit skill and then purchasing "domains" (Hawk domain, flower domain) with talents that would grant expanded usage but it seemed needlessly complex, and I feel this works better because it means an elder tree spirit would have less dice when dealing with a minor domain outside of it's primary focus.
I'm working on coming up with thematic renames of the attributes, namely for Brawn and Agility, just for flavor.
Now I'm curious how much I'm going to worry about adding the interaction "layers" of spirits. Will players need to augment weapons to affect spirits? Do spirits have diminished power if they are "dematerialized?" How would I handle that, give setbacks on all skill checks if they aren't materialized?
Interest/comments/critiques?