Inkscape handles linked SVG files just fine... it just doesn't provide a friendly interface for creating the links. So if you already have a bunch of SVG files that just need converted, Inkscape should handle that. If you want to create new SVG files, you can do it with Inkscape, but you have to edit the links in the XML editor by hand. Kind of a pain if you're wanting to do a bunch of map symbols or something.

For map symbols, it turned out to be more beneficial to build my library of SVG symbols and write a script to convert them all to PNGs to use in my maps. That way, Inkscape doesn't have to re-render the blurs on all the imported objects, which speeds up the display considerably.