Actually for the hair, all blending problems can be solved by first rendering the head with depthtest and zwriteenable set and then the hair with zwriteenable off and alphablending on, if you need more than one hair layer, most (?) modelling tools allow to sort the face indices and thus the polygons rendering order by for example their distance to the center, if you do this from the inside to the outside, it should just work (at least if MED doesn´t destroy that order later on...).
