Enrique,
Our issues here at Sloan are slightly different and so I hope you can accommodate thatm in what you plan to do. In our case, I close each class at the end of each term so that it is no longer available for anyone new to join it, but unless I am asked, students are not removed from their classes. And i do not use the 'archive' function for classes for the same reason - for the most part, our professors do not mind if their students retain access to class materials after the end of the term and actually, students really like this 'feature.' I think we need to change the way students access content from previous terms, but we haven't gotten to that yet (and by this i mean that we need to expand the functionality of the Join/Drop page to include browsing by term).
So, though some of what you propose - an automated way of expiring classes and the ability to make content read-only - would be very useful to have, i would want the option of allowing students read-only access to their old classes as well. Would you be willing to include this as an option?