i join the brainstorm :) i was impressed lately by this feature of excalidraw: embedding raw data into an exported image
https://twitter.com/excalidraw/status/1316001446043750400
https://twitter.com/dluzar/status/1316005742512607232
the idea: export from annotorious an image (png) with drawed boxes with annotations. the export contains also json web annotation data.
reimport the image into an annotorious setup, it will open the image (static or iiif) with editable annotations.
maybe this exceed the scope of annotorious and is more into generic IIIF viewers