The system is only overconstrained if all the bodies are rigid. It's okay if there is compliance and the WP may be considered the compliant member.
If the WP is very rigid, then you can design in compliance in the two DOF that are overconstrained.
One example is two flexures at 90 degrees. The orange face would have the three Vee slots that I haven't drawn. The two flexures allow the orange face to rotate about Y and Z axes so that the other end of the WP can align with the connection at that end.