I can't help but comment on a blog post I saw by Rob Newby the other day. Struck a cord about how paranoid the regular security person needs to be........
His original post is here: http://robnewby.blogspot.com/2007/03/one-of-us-has-to.html
If you're worried about collusion and superadmins with access to everything you're a bank, a defense department, or paranoid.
Not that a single "superadmin" should be able to anything by themself, but I'll skip that point for now.
If what you're looking for is protection against all of the scenarios you've outlined then you're not looking for commodity hardware, operating systems, physical security, etc.
Maybe you ought to consider not hooking the system up to anything. And bag checks at the door. And periodic interrogations, surveillance of the admins, credit checks, black-bag jobs to break into their houses, etc.
If you're really worried about multiple people colluding and walking off with the data, then you're going to need more than logging and hope to achieve it.