Whilst out shopping today my mind started thinking about things. While its great that we can now mirror an entire guide it would be great if we could mirror only bits of it. For example mirror only pages about croydon and set up croydon.openguides.org. then fiddle with the templates so thats edits (and possibly new pages) get sent back to the main guide (london.openguides.org). Admittledy this new guide would then have to create soem of the pages itself for instance the category_pubs page would need to say different things to the original so in fact you might need to have two edit functions. im sure it oculd work or soemthing.
So the extension would be to tell mirror.pl that you want to mirror only certainy categories or locales and disregard anything else.
Shame i cant code :)