The extension could potentially start modifying the revactor_actor field in the revision_actor_temp table, or eventually, the rev_actor field in the revision table (after it is time to get rid of the temporary tables named "revision_comment_temp" and "revision_actor_temp").
It could also allow changing the author of deleted revisions in the archive table directly without having to first undelete them.
Of course, author changes can easily be reverted. Actually, there should be a "revert" link next to each ChangeAuthor log entry. The author of log entries themselves cannot be changed.