I was happy to see that the Animation Rigging had some IK constraints. For more sophisticated uses, what I need is a FABRIK solver that has individual joint types on the chain. Specifically limits in degrees of freedom at each joint.
The conical example is the Final IK asset which implements this very well.
Is that possible now in some way I am not seeing?
Hi nsxdavid,
The current version of the chainIK shipping with the package only implements the unconstrained FABRIK solver. It would be nice to eventually support the constrained version out of the box at some point. In the meantime, you could always implement the algorithm using the animation rigging toolkit since it was meant to be extended with custom constraints.
I’m definitely craving some spherical constraints too - after looking at the video and slides on how to code your own constraints:
…I’m excited to try. I’ll share any success I have. 
Cool, but don’t forget to try prismatic constraints too! Those are arguably easier to code anyway.
I saw multi Aim constraint have some rotational constrains. Definitely there is need for joint constrains, spherical, pyramidal and curvical as in Final IK. TwoBones IK seem very basic, not efficient for Human animations, cause as in demo, need of additional target, hint and bones animation, when can’t be solved with those constrains.