Sébastien,
I am currently understanding that it should be possible for LibreSource to be configured for a resource to be the "view page" of a subversion repository.
So I would expect to find a possibility to add a "new subversion repository" as one resource type; in there one should enter the simple mod_svn URL and the rest would be transparent: notifications, history browsing, ...
Externals (svn externals), would then come as a fancy artifact to create artificial mod_svn URLs to encompass several others.
Do I understand that my first supposition is wrong?
thanks in advance
paul