Assembly4 and SubShapeBinders make it possible to assemble Parts, then using their position in the assembly to generate new Parts. However because new Parts depend on Parts in the assembly, if you try to add them to the assembly FreeCAD 0.19 will complain about cyclic redundancy, which makes sense.
To get around this, one method is to change the Bind Mode of the SubShapeBinders to "Disabled" which copies the geometry but unbinds it from the base object.