One option (which credit card companies would hate) I feel would greatly benefit the owner of the credit card compared to authorized users, if there was some sort of approval process for charges on the card.
Let me provide you an example:
In your online banking / credit center, there would be an AU options page you could access. One of the options would be to set a maximum transaction amount per item. For instance, setting it at $30 would mean that the AU on the card, could not make a single purchase larger than $30. If they try to do this they would be declined. That would put the mindset of the student of not being able to make any large purchases which could jeopardize the card holder.
Now something that might be completely farfetched at this point would be if the AU tries to make a purchase larger than $30, an instant text could be sent to the card holder with the ability to reply to approve the transaction. This sounds all well and good... but you don't want to be sitting in the check-out line for 15 minutes as you wait for an approval. But hey, that's just t a thought! :)