independent mirrored components possible?

I have a component in an assembly that I need to mirror. Atpresent the components are true mirrors. However, once I mirror thecomponent I want to add features, additonal mounting holes and apocket for a sensor that is not necessary on the parent part.
What is a good method for achieving this?
Can I add the necessary features to the mirror without affectingthe parent?
Can I create a truly independent mirrored part?

Thank you for your input.SolidworksAssemblies