Workflow Question: Components, Patterns and BOM
This is a tough one!
The way I would approach this in any of the other CAD packages I am also familiar with (SolidWorks, Alibre Design, ZW3D) is by using Configurations. Usually that means feature configurations, dimensional configurations and assembly configurations. Unfortunately Fusion 360 still does not have that feature set implemented (they are working on it ).
Some workarounds exist that others might find useful, and hopefully might post.
I am sure you are aware that in order for items to show up one the BOM you will need to work with components.
Patterning an move/copy will create component instances. The original components contains the one data set and all the instances are pointing to that data set.
As such you cannot modify an instance without modifying all other instances.
You can also not convert an instance into a stand-alone component that can be individually modified.
You can go back into the timeline and copy-paste-new. Then you can use the remove feature on the instance you want to replace and assemble the paste-new component in that place. However, all the stuff in that now independent component needs to be edited separately, unless you are able to work with user parameters that you can use in any component.
This situation can get messy ad unmanageable depending on how the timeline in your design and how you set up your design from the beginning.
I forgot to answer one of your questions.
Mirroring will always create a new component. Mirroring might sometimes seem convenient, but it will bite you when you then create the BOM as it does exactly what you want to avoid. It creates two separate components on the BOM with an instance counter of one(1) instead one component with an instance count of two(2).
