Elementalist is a very complicated unit, which I see is your specialty.

I haven’t added it yet because I have questions and/or reservations about some of its features.
I’m not sure how you envision Elemental creature(s) in this game. I see them as monumentally powerful, equivalent to level 5+ on the current scale. Something on par with forces of nature expressed through earthquakes, tsunamis, volcanic eruptions, etc. I haven’t added them to the creature lineup as yet because they don’t fit the established mould of living in dwellings, being trained, etc. Nor can a magician simply conjure them up; their size and scale are too vast, their power too great. It would make sense to me to make them summonable by a group of wizards working together, with the right combination of spells/artefacts and terrain, but I haven’t given the mechanics enough thought at this stage.
Making it an “Elf + resources” unit instead would be problematic because it would give the Sylvan player access to a level 4 unit from the start.
I would generally prefer to use higher-level magical creatures instead of an Elf. Main candidates would be Morg (level 2), Djinn (level 3) and Angel (level 4). Possibly Lich, Deva and Demon as well. My favourite would be Morg because this is the main protagonist of my fantasy novel.
The complexity of using the unit makes me think that it would work better as a hero. This would enable it to learn spells and wield artefacts that would grant it these abilities. Generally speaking, I would prefer to build up complex abilities in lego fashion than to have them innately present in any single unit.
The game doesn’t currently distinguish between physical and magical defence. This has been working well enough so far, so I’ll probably keep it that way.
With all this in mind, I’ll put the unit on hold until I have a better grasp of the game mechanics.