So here’s the first part of the idea: when you do an export, have an option to immediately open that export file in the default .csv editor. Sorta like the download save / open dialog in your favorite web browser.
Bigger idea (after using command line tools for Subversion, Perforce, and the like): send the export to a temp file, open it, and detect the close of the editor, at which point you reimport the temp file. For example, try the Subversion command line svn commit without a rev note specified. It will open the rev note temp file in your configured editor and wait for you to close it, then parse the file. Hopefully that makes sense…
So you could do an export, fiddle with it in excel or something, and have it reimport on close. I think that could be cool.