The short answer is no. With the WP import function, you must leave the importer uploads the xml file for you... There is no way to upload it by yourself via http://FTP... The import function only gives you the possibility to browse and choose a file on your computer.
What problem do you have with the directory permission ?
Any decent ftp client will give you the possibility to chmod the "uploads" directory in wp-content/ with the right permission.
Then, after, if you feel insecure about this permission, just set it back the way you want...
But, if you use the file uploads function of WP, you will still need to leave it at 755 or 777...