In today's miniature rant on "why the heck do I need to jump through 5 separate layers of abstraction to make this happen in C4D"...
I think, though I'm not quite sure yet- that I at least have some sort of a usable solution in place for dynamic ponytail rigging. If this doesn't look very impressive, it's probably because it's not. There is absolutely nothing particularly special about this setup, since it's literally just a barebones Spline IK rig driving some hidden proxy geometry within the scene.
Most of the annoying evil stuff is figuring out what to do with that data after the fact, since just about every single tool in C4D is designed to not let you rig hair like this. It takes no less than three custom plugins to make this work, all of which I'd fortunately written back when I was messing around with Vanessa's autohair rig (which unfortunately didn't work out that well because long hair cannot be easily rigged in any sane fashion, but a single flexible ponytail can).
Anyways, I'm hoping this will be good enough for now. At this point I kinda just wanna get this character done and working so I can get back to rendering stuff and working on a new image sequence, since I'm not really planning on dealing with C4D any longer than I absolutely have to at this point.