Managing offline members

I need the ability to view offline members so I can manually purge users who haven't been online in a long time. The purge function is useless since every member who agrees to the rules is assigned a role upon joining. The members list in settings only shows online members as well, so that's no help. I understand it's a processing issue for mobile users, so maybe make it browser only, and split the users into pages? Offline members shouldn't be inaccessible.