I do some taxidermy work. I once mounted a doe w/antlers for a friend of mine. The remaining velvet was just like your pics. All dried on, some flaking/peeling off. Its beyond preserving the velvet at this point. What I did was put some "Liqua Tan" on the antlers, to sorta hide like tan what was left of the dried velvet. She came out good, and last I knew no remaining velvet had come off. Mention that to your taxidermist as a idea, or maybe there's something they'll know I don't.
Def. a sad story to a very cool, unique deer.
Oh and far as the velvet left on by the doe. A doe doesn't have a bucks instincts to rub tree's to remove the velvet!!