I have the same questions.  As I understand it (and I'm not all all sure that I'm right), you can only reset the password for all keys at once.  However, that password must now be very long (32 characters, I believe).  

Once you've done that, I suppose you'd then make note of all your private key WIFs.  You'd keep your master password and your owner key WIF in cold storage and never use them.  You'd use your private Posting Key WIF to log in for normal activities and your private Active Key WIF to transfer funds or buy/sell.  

The trick to preserving security would be to keep your master password and your private owner key WIF in cold storage and never use them.  Since the master password is so long and never used, it should be safe (I suppose) to use that same master password with all the keys rather than having a separate password for each key.  I think people were previously recommending separate passwords for each key only because people were logging in with passwords rather than WIFs.  If you only login with WIFs it should be fine to have a single super long password for all keys.  

If anyone has any more info on this subject, or disagrees with my assessment and explanation, I'd love to hear it.