Great link gmendieta!! I’ll have to bookmark that!!
Some of this can be done without python, but in a limited way, see attached file. In it, I created a simple fk/ik arm. If you select the handIK bone, in the transform panel, under Properties, you’ll see a box that says ‘FK - IK’ and a number field next to it, that is the fk/ik switch for the arm. When it’s at 0 the fk arm has it’s own pose, when it’s 1 the fk arm copies the ik pose and in this case I’d use the fk bones as deforming bones. So it can be done without python.
Python can improve this setup and add so much more pretty easily, it’s not much code. Take a look at my Joe rig in my sig. He has rig layers in the UI and fk/ik switches if the selected bone can be switched to fk or ik. In my example posted here, the switch can only be accessed when the handIK bone is selected, with python, the slider is there when bones that can be switched are selected.
The script that does all this in my Joe rig can be found in the text editor with the name Joe_Rig.py and is less than 100 lines of code…
fk_ik_switch.blend (334 KB)