We have discussed this before, and if I remember correctly, the issue with the idea is that without PSDs of the Soqs getting "haircuts," the colorist would basically have to do an entire recustom.
For example,
long manes (and other hairstyles) cover part of the horse's face. Going from a long mane to a braided, short, or pretty much anything, really, would be impossible without erasing the mane from the face and having to recolor it. And since most colorists don't keep PSDs of the ponies they've colored (I can't even imagine how much hard drive space that would take up), it would simply not be feasible or realistic.
I'm just spouting things I remembered from the last time this came up. You can read the full thread
Here.