I tried to activate the plugin but I got a fatal error :
Fatal error: Using $this when not in object context in /homez.467/escadron/www/wp-content/plugins/archivist-custom-archive-templates/archivist.php on line 319
It seems that you use a $this while you're in a static method.
Well it's a pitty because your plugin seems to be excactly what I need ! I didn't test with previous versions of it to see if it was working.