Create a Hyper-Blog for a Multisite feeded with the posts of every blog in the Network

Hi
I am planning to set up a network of sites based on the same general subject (promotion of Galicia (Spain NW) as a destination). Each site will be focused on a main aspect: folklore, nature & culture, entertainment... and will have its own (sub) brand linked to the main site brand (Galike). Thus, I will be interested in setting up a configuration like: galike.es/name-of-the-brand-for-entertainment-in-Galicia; galike.es/name-of-the-brand-for-folklore-of-Galicia; etc. Each of those will have their own blog ( galike.es/name-of-the-brand-for-entertainment-in-Galicia/blog...), but I'd like still to have a main blog for the whole network (galike.es/blog). I was wondering if there is a way / plugin / workaround that allowed to show in the main blog a feed of every blog post in the network BUT without making a copy of the post (to avoid SEO concerns for google penalising duplicated content); so that the main blog would work as a mere frame filled with the posts published from every site of the network...

Thank you
Pablo