Kahga had so much potential. Way more than Halsin, IMO. The fact that she could be evil or repentant depending on how you handled her quest would make her a pretty unique companion if Larian went that route.
Nettie. Like Kahga has better reasons to leave the grove than Halsin, but more of a nicer character than Kahga. Pus a sort character, which we have no companions of currently.
Nettie would be an option.
She seems more like something very simple and as a story character somewhat typical of the story.
If you could give her a role, then that of a rather healing druid, with a special druid role that includes more natural healing and a special shapeshifting form, like a forest nymph or dryad, which then has as abilities many healing spells and regenerative spells, as well as protection, for example, bark skin, poison resistance or something.
Since she acts as a healer in the grove, I could imagine this as a possible Nettie variant.
Otherwise, I like Kagha better thematically because she's more complicated and thus has a deeper story component.
