Hello Codre,
sound like an option.
Several month ago the developer of JOOMSEF wrote me via mail (as answer to my questions how to get rid of JoomSEF and keep Joomla working)
Hi Stefan,
If you want your JoomSEF generated URLs to keep working after you uninstall JoomSEF, you can either use Joomla's Redirects component or your web server's .htaccess file to manually setup redirects from JoomSEF SEF URLs to original Joomla URLs. You can obtain list of SEF URLs with their corresponding Joomla URLs from your database, their stored in the _sef table.
With kind regards,
I have several thousands redirects too and manually it's not possible, so I guess an solution to get the urls from database and modify them to fit into the .htaccess would be an option too.
But maybe it's another problem if the .htaccess is too large