I think it should just be fine if we define a different workflow (and thus different labels) for external projects...
The 'Area' field looks unused, having only a single option 'Misc'. Perhaps that could be 'Image' and 'External Project' or similar. Most of an external project's issues would also have an area of 'External 'Project', but sometimes it might be 'Image' if a change there is required to fix an issue reported on a project. Or maybe for external projects you have only a single option 'External Project' for Area.
So we need to have 2 things 1. a separate project for each external project that wants to report 2. a separate Area for these external projects For instance, NativeBoost has both a stable version in the image and a development version aside. So if a bug appears in the image we can set the Area to "Pharo Image" (the default). However, if the bug concerns the development version we set the Area to something project specific. I will try to update the tracker and the filters to reflect that...