Well, before I let the subject drop off the face of the map, let me throw out some reusable code ideas:
A rich text editor gadget that can column-wrap text to another instance of itself would make simple DTP style editing of documents possible though Scribus is enough of a DTP for professional use already.
A metadata-aware file BFS derived media database that could be expanded to a serialization file format and network filesystem would make a nice feature. It wouldn’t be SQL style but would complement existing file formats like Oasis OpenDocument XML file formats do for LibreOffice. The downside is the requirements for this are vague and LibreOffice uses Zip to compress its XML already.
About the only thing that spreadsheets do that sets them apart from databases are the charts and graphs being generated more easily and having a generic user interface. What would happen if a GUI builder existed that could make a spreadsheet into a more specialized database format like the BFS idea? Like I alluded to earlier, it might not kick SQL to the curb but maybe a MongoDB/DocumentDB wrapper would be useful.
Other than that, the replicant idea works for me.
Edit: I see MongoDB Compass is available for Node.js so that might help.