Many ubiquitous tabards are featured on “tabard vendors” across Azeroth.
With the introduction of faction tabards that award rep in WOTLK, I imagine there are many more instances of people deleting extremely rare and valuable tabards without thinking.
Most of these extremely rare and now unobtainable tabards are 1. not featured on the tabard vendor and, 2. of common quality so they cannot be restored through the item restoration feature.
Given these two facts, might it therefore be a good (and relatively simplistic feature) to add more such tabards to the same tabard vendor.
For example: tabard of the argent dawn