multiple conferences

I suggest to allow multiple conferences to be shared independently.
There would be a "create conference" function, and to each conference might be associated a specific content type for papers and reviews.
Through creation of specific roles, participants can easily be "attributed" selectively to one or another conference.
(Often it is nice to have the list of previous conf participants for an upcoming one - they could be automatically be invited to sign up for the next one.)

Finally, an "archive" function would be nice which creates an archive file with all relevant material of a "finished" conference, so it could safely be deleted from the web site yet still be available as collection of portable e.g. PDF and/or X(HT)ML files