Outer skin
My suggestion to NASA after the Columbia accident was to create a thin Kevlar skin that completely encased the tile area. The skin would be molded to exactly fit over the nose, underbelly, and wingtips for protection of the tiles during ascent. It would add some weight but probably not a great deal since it wouldn't take much of a thickness at all to protect against flying foam.
On reentry this layer would burn up quickly and not be a problem.
Art