Chazelle-style Soft Heaps would be a great addition to this library. They are asymptotically optimal for a different class of problems than the Brodal/Okasaki heaps, and while a functional implementation cannot delete non-minimum nodes with the same O(1/epsilon) guarantee, you don't need that functionality for many of the algorithms that this structure is suited to. (soft minimal spanning trees, near sorting, exact selection with soft heaps, etc.)
Chazelle-style Soft Heaps would be a great addition to this library. They are asymptotically optimal for a different class of problems than the Brodal/Okasaki heaps, and while a functional implementation cannot delete non-minimum nodes with the same O(1/epsilon) guarantee, you don't need that functionality for many of the algorithms that this structure is suited to. (soft minimal spanning trees, near sorting, exact selection with soft heaps, etc.)