How can I duplicate a network in english ?

Hello,

I am trying to build a multi site that will be one main site with buddypress and 3 subsites.
all in French.
I would like to create later, the same facilities in English without having to create 2 separate neworks, but keeping the ability for users to switch on and of english to the french community without having to log out.log in each time.
So in summary, same user base, same buddypress profile that will need to appear in French/english.
So what are the best to do this ?
2 different buddypress install ?
Or one only, with profiles translated, and activity streams form both english and french sites ? possible ?
Best regards,
Hervé

Best regards,