Direct3D made it be introducing a new kick-ass feature called GS, though not available on every HW at the time of release.
Lets have the ability to instantiate new fragments with different positions and possibly colors based on a fragment generated by the rasterizer.
Lets call it "Raster Shader"

Or make it part of the FS, by adding something like:
gl_NewFradCoord[1..MAX_FRAGS]
gl_NewFradColor[1..MAX_FRAGS]
MAX_FRAGS implementation dependent on how many frags can be instantiated per rasterizer fragment.