I've been chatting with someone about cosplaying Kaede (from Inuyasha) and came up with this idea for her friend with lots of long dark
hair.( Diagram behind the cut )
The basic idea is that for a person with a lot of hair a wig might be a bit of a hassle. Since Kaede (and several other characters I can think of) ties her hair in a very low ponytail there's theoretically room for a snood (a cloth or net sack to hold a person's hair) above the tie.
Now if someone were cosplaying Kikyo and already had long dark hair (long in this case being sufficient to bind into a tail at the appropriate point) this is overkill. If their hair is dark and long enough then all they really need is a (possibly modified) Halo frame (if they don't want to cut fringe) and some wefted hair to match their own hair to add length to the ponytail.
Getting back to the snood-wig, it could also be used by someone with shorter hair if they wanted to have something lighter than a full wig (since even old lady anime characters have huge amounts of hair it seems). They could just add some stuffing to the snood (and possibly a small weight in the bottom to make the hair behave more naturally).Disclaimer:
I have not built a snood-wig so this is all theory based on my knowledge of things like wigs and sewing.