Currently the database dumps are configured to skip certain tables altogether due to privacy concerns. For example, the user table is marked private entirely.
The user table contains a number of columns that are not private (e.g., user_id, user_name, user_registration, user_editcount). These should be publicly dumped.
The same is true for the ipblocks table, which has a lot of columns that can be safely exposed.
There may be other tables that can be safely exposed, I haven't done a full audit.
Main page on the topic, with use cases: https://www.mediawiki.org/wiki/Research_Data_Proposals