I was recently playing with this app: Service Station and thought - I like this, but would prefer if this functionality were directly accessible in KM.
The idea would be to have a "Trigger" of type "Finder Contextual Menu". You could then either set it to work for specific file types, or allow all. Then in the Finder it'd show the macro when you access the contextual menu.
I'm aware there are other ways to accomplish this: Services menu, or even using the Service Station app I could trigger an AppleScript to run a KM macro, etc - but I think it'd be a useful trigger to have in KM to make the process seamless and managed in one place. (Nothing I dislike more than depending on a hodgepodge of different apps/services)