NoD,
The tile system on all the shuttles is standard. However, each tile is unique, fitted to its particular location on the shuttle. The thermal protection offered by a tile also differs, depending on the temperature regime it is expected to encounter on re-entry. So one could not stock 50 or 100 tiles on the shuttle as spares and stick them wherever one wished, as the likelihood is that they would not fit.
Typically, about 50 tiles are replaced after each flight because of damage. The damage usually is caused by debris strikes during launch, or in-orbit strikes from micro-meteroids or space debris.
Airship, the orbital inclination for this last Columbia was 37 degrees. The ISS is at a 55 degree inclination or thereabouts. While George Lucas can easily maneuver his starships between such inclinations, real-world spacecraft would find it nearily impossible to shift inclinations to this extent.