Gonna throw in my two cents in here because I think I have a very different idea about what a polymorpher should do.
In my mind, polymorphing has to be a difficult discipline. You can't just change willy nilly or you get stuck that way, and if changing yourself is hard, then changing others must be extremely difficult. As such, I'd like it if these abilities focused on self improvement and using beast/monster-like abilities to your advantage.
In my opinion, this class would be best served as a melee caster. Abilities which act the same as say a bleed slash from a warrior or rogue, but that increase in gravity as you climb higher in the ability ranks. For example, at novice level, you would change your hand into a claw and deal the bleed that way, or change into say having a turtle shell and you protect yourself for the turn. Then as you get better and bigger skills you get to the point of changing your entire model for a couple of turns and obtaining the abilities of that beast. A removed skill from classic Original Sin was I believe called phoenix dive which was a warrior skill that allowed you to traverse the field and deal some fire damage. This skill could be reused for this class, and make others like it. However, I understand how difficult such a thing would be to actually implement into the game (the sheer amount of modeling and animating would be staggering, not even mentioning the coding), but this is my wish for it.
As a compromise, I think simple "beast master" type skills would be awesome, with shapeshifting in there for wow factor, especially at master tier. I liked a lot of the OPs ideas regarding skills which would grant a passive effect, I think it fits the theme really well.
Regardless I know Larian will do a great job, I just hope they have the time and money to implement some community suggestions as well
