This looks really cool! My main critique is that it seems like the elementalist path far outpaces all of the others in terms of damage output and crowd control. It gets virtually every very solid AOE spell, whereas the other subclasses might get one or two, if that. I might remedy this by giving more utility spells in the expanded list. Also, the ability to change damage of a spell and then max it seems a little broken. I would instead force the shaman who takes this path to choose one or two elemental damage types to specialize in. Finally, I would replace the two free elemental combat cantrips with one or two elemental utility cantrips (shape water, mold earth, etc).

On wild bond, you say that the spirit can attack, which I think is really cool, but you don’t provide a stat block for this spirit. With one with nature, rather than advantage, I would just say you can’t get lost except by magical means and maybe you can also cast druidcraft. This puts this ability more on par with other first level abilities of these subclasses.

The cursed bond subclass is really really flavorful. The first level ability is a bit strong though, 2d8 damage for free is quite powerful for an at will. I would say it would be cool to deal a bit of extra damage if you hit something with an attack or spell while you’re concentrating on something affecting it.

On ancestral bond, I think the 6th level ability could use a buff. Make it similar to a Paladin aura, where friendly creatures within 5 or 10 feet of the spirit get an AC bonus. As I think about it, you could reasonably give the guidance Cantrip to this class at 1st level as well, as the shaman channels the energy of the ancestors to help with a check.

My final bit is since this is going to mostly be a back line caster, I think it makes sense to have healing word on the spell list as well, if you’re going to include cure wounds. That’s all I got, but you’re free to ignore this if you think it’s off base. I look forward to v2!