Concerning heat-resistent tiles, I just remembered something I read a couple of years ago. The Russian shuttle-program "Buran" was apparently using some other carbon-based material that was more heat-resistant and stronger. I checked, and the web-site still exists:
http://www.buran.ru/htm/molniya5.htm
The website is a bit slow, but it seems the russians had a few ideas about how to make a "better" shuttle. Maybe some of their ideas could be incorporated to make the american shuttles safer? Would love to see Buran fly alongside the shuttle in the future, but I guess it's a bit unrealistic...
The show must go on.