Moodle networking (MNet)

Can anyone think of a reason why this might be difficult to implement? I appreciate the barriers but cross-moodle course lists seems like a logical addition to Mnet

As a side note: I am hoping to establish a shared course list by using external enrolments database which will either hold the ID number of the courses to then create links for a My Courses list or query the db on load to do the same thing.

I.e. User logs into main MoodleA, course list checks their enrolments on MoodleB via external db, Course List populates an entry for each enrolment on MoodleB as a link to the course in question + tutor info and course description. This might all be hard coded ...

any ideas??