Mark,
Just another stupid idea, but what if they move the Shuttle about 2 or 3 feet farther away from the tank, so if anything comes off it will miss. I think the chunk that hit Columbia would have cleared in that case. They would only need to re-engineer the structure between the tank and orbiter, the attachments would basically remain the same. It would only change the flight dynamics slightly and they could reprogram the Shuttles nozzle angles to make up for the slight change in configuration. I believe they have it engineered now so that the Shuttle thrust and SRB thrust matches very closely so there is minimal stress on the attachments, so a little longer attachments shouldn't cause any problems. They could do an analysis to confirm that it would be impossible for any foam to come far enough away from the tank to hit the orbiter. What do ya think?