As demo’d in this video: OR3D tool walk thru the video is a bit on the older side, but it shows the IK fairly well.
the system is fairly simple rig that attaches as a script to the IK End Effector, and parses up the hierarchy collecting any bones that are tagged with a certain empty class (In my case called an EndJoint).
I collect bone joints at runtime after combining and configuring the hierarchy, and pass them into the CCD IK function as an array of unity transforms. the bulk of the code is taken almost directly from Jeff Lander’s game developer article describing the Cyclic Coordinate Decent (CCD) inverse kinematics algorithm, written in 1998,
the port can be downloaded from here: IKCCD2D.zip