I don't know much about this so will be learning with you as we go along.
However, I see there being two phases here - (i) being able to launch a firejailed version of a specific LibreOffice Calc spreadsheet from the command line; (ii) associating the .ods file extension with that command (probably by playing with the .ods-related MIME type and/or the LibreOffice Calc .desktop file). With which of these are you having problems?
Another thing to consider - would you be content with being able to right-click on the .ods and launch the application firejailed from the resultant context menu? This would save having to change .ods MIME associations and desktop files and is doable depending on your file manager.