Poking around the source code to see how I might add some workflow steps that would nice for my org, I couldn't help but notice that the existing components and their UIs are hardcoded, wherein any additional or modified components would require a rebuild.
What if the workflow components were bundled separately from Imagr.app as something like plugins or bundles? One still authors their workflow plists with included or custom components, making sure to include their custom components at some location. This way, Imagr becomes a runtime and the community can create and share components.
Other opinions aside, it's a lot like deploystudio's architecture - which is working pretty well for their own workflow steps.