The other Dullahan I can think of is from the Monster Girl encyclopedia, but we already have dullahan and disembodied_head tags. Judging from the variety of posts using these tags, I think a pool would be overkill.
Edit: Misread your suggestion, but I personally don't think we'd need a pool for Dullahan Sekibanki. My argument would be it's too narrow to warrant a pool.