This functionality would work for any equivalent link associations. I am using equivalents links to manage color parts. I have a color neutral CAD object with an engineering view Wt Part associated via an owner link. My color parts are in the manufacturing view. There is an upstream / downstream equivalent link between the engineering neutral part and the manufacturing color parts. All parts are unique part numbers. I call the color parts "Siblings" of each other based on the fact that they are all equivalent to the same upstream part. Since the upstream/downstream relationship exists, I should be able to select a color part in a structure and replace it with another color that is downstream of the same neutral part. Hence, Replace with Sibling. A window should appear that shows all of the options (siblings) that are available. And added feature would also include the option to create a new sibling on the fly if the option you need does not exist. The newly created sibling would automatically have the equivalent link in place.
The benefit of Replace with Sibling is to perform a Save As from the parent assembly to create a new variant and quickly update it exchanging the lower level variants already established by equivalent links. This feature can be utilized at any level in a structure and, as mentioned earlier, can be used for any type of equivalent association. This functionality would aid in BOM creation as a transition step before moving to Options and Variants.