If I understand yes, you can have shared data and then just use the category shortcode option to limit the results to a specific category.
Is the site a single site now? I think if you add define( 'CN_MULTISITE_ENABLED', FALSE ); (in the wp-config.php file) at the same time you convert to multi site … everything should just work. Honestly though, I’ve never tried it.
If you already have multi site setup, you still need to add define( 'CN_MULTISITE_ENABLED', FALSE ); to the wp-config.php file.
Will you lose or have to re-add your data, no … but, you may have to move the connections-images folder to the correct location and use phpMyAdmin to renamed tables so they are associated with the super network tables and not any of the network sites tables.
Hope that helps!
