Jettisonable Leading Edge Material or Fillet?
RobertS975
You have to work out a risk-management philosophy that's weighted toward the the greater threat (launch debris damage or launch abort).
a. Engine failure aborts, if some engine power/thrust remained, the Orbiter's aerodynamics wouldn't be degraded unrealistically by a wedge-shaped protective inboard leading edge. Many jet aircraft sport those for improved spin-stall characteristics. You'd probably only need about two metres per side in order to protect the very vulnerable areas of the wheel-well in particular. The remaining outboard span's protective sacrificial overlay could be a conformal section (not wedge-shaped deflective).
b. Alternatively, for the highly vulnerable inboard areas, a jettisonable false section similar to a fillet could be fitted. An in-atmosphere emergency jettison of that could be as simple as an explosive bolt each side at its leading fuselage attachment point. In the event of an abort they'd peel away with the ET and SRB's. For re-entry, it would be pre-jettisoned (or it could simply depart by design with the ET or SRB's, its protective role being superfluous by then).
It's not really rocket science, it's just a matter of protecting what demonstrably post-Columbia needs to be protected / needed to restore confidence / is required to avoid the necessity for complex in-orbit inspections.