This paradigm reappears a lot in Corona Renderer development (i.e. "It is always better to err on the side of offering more control to the user"), but it isn't a bulletproof approach in the context of usability. Mirroring features across a feature set isn't unreasonable, and in the case of the CoronaBumpConverter, it would literally be matching a feature that already exists in a parallel implementation, namely the CoronaNormal Texmap.
I view the CoronaNormal Texmap and CoronaBumpConverter Texmap as sort of companion (parallel) implementations for shading bump detail either through an RGB or greyscale map, respectively. The CoronaNormal is required (default) for using normal maps with Corona Renderer. The CoronaBumpConverter is NOT required for using greyscale bump maps, but it does facilitate their use.
I think what I'm considering is a way to obviate the CoronaMix node for a situation in which a surface is defined by a greyscale bump map, but there is a need to enhance that surface bump with at least one more greyscale bump map.