Material Replacer
Can I replace any material with any other material?
No. Currently, there must be two materials with the same name when appending materials in your scene. IE: "mat_body.001" will replace "mat_body" and be renamed.
How do I install?
Navigate to Preferences and Addons in Blender. Install the "material_replacer.py" file. In the 3D View, press "CTRL + N" to show the tool panel on the right-hand side.