Hello!
Sorry for resurrecting an old thread. Just writing to say that we are interested in a solution to this as well. On our multi-journal OJS, some journals want to have more control over what is being presented on their website. If an author is registered to several journals, removing the biography from user is not a good solution.
Theme modification should be simple, but would prefer a built-in solution that can be managed by the journal. So a +1 from me as well 