Back when the MilHorse came out, there was a suggestion that the next time, the mane should be made a conformer - like conforming hair rather than built into the mesh.  Did that turn out not to be workable?  Seemed like a great idea to me.  Maybe have a short, cropped mane built into the mesh, to help the conforming mane blend in in extreme poses, but most of it be like conforming hair.