Actually some of Koz's hairs already has that morph included ,or as a separate MT...
Like "Short bob" hair has an "Invert" dial and "Messy"and"Long Evo" have an invert MT for download on his site.

You can make them (morph targets) yourself for other hairs, with one of the free programs (like Wings).
Just need to mirror (flip) the X-axis.

SWAMP