Yup. I strongly agree with you on this.
Going file-hunting for that missing image is no fun so any way to automatically collect them all for shipping to the print house would be great.
I've actually never heard of a print house using Inkscape (or any FLOSS product for that matter). Do you have their web address or e-mail? I'd just like to ask them a few questions about Color Management.
Hence I think that an option that parses the SVG file and generates a
tarball with the SVG, its associated images and the relevant font
faces would be very nice to have.