Might be problematic considering the gameplay effects, but I really like "Living Minerals" as non-Food race, that instead grows by production/energy (as they mine and imbue new Population instead of giving birth). They'd have Arc and Heat as damage channels obviously.
Also I'd love the sentient plants of the growth to become a Major faction. They technically would have biochemical and kinetic, but generally the tech-based mods don't really fit too well. Maybe that is because we have only humans and very humanlike factions...
Basically, the more "inhuman" a race, the better for me. Currently that's Dvar and Kir'Ko, but I'd like more.
The Psi-Fish as aquatic-based Major faction would be great as well, I love the design (like in the movie "The Abyss").
Amazons got the "tribal" type covered pretty well, though I could live with some Kind of high-tech shamans as well

Sort of Space Orks/Ogres would be fine as well, that usually roam around in wastelands. Though Spacers would have quite some overlap there I think.
Apart from that I'd like Cold to be added as another damage channel, everything from ice rays to localized Blizzards, debuff would slow, obviously. That would allow for a humanoid snow-Bison race. They could be the "shamanistic" faction as well (think the Banuk from Horizon Zero Dawn).
Also, an actual Hivemind faction is missing at the Moment IMHO, which again, the Growth would bring to the table. Apart from that Immunity to Morale (Positive and negative) and mind debuffs/Control, as no unit has any form of Motivation or a sense of self. Think W40k Tyranids.