Obviously your solution needs both the rewrite-code and the plugin.
Why not just using a plugin like
I know why it is necessary... DC and loosing backlinks.
But I still don't know the best solution in my case...
And I still don't feel good with using a 301. Nobody shares this feeling using a Url-migration-tool in order to keep up the Urls?
A plugin on the other hand makes me dependant "for lifetime" and there will be changes of WP and the theme.