Hierarchy management solution(s)? (node or taxonomy)
Yes, the wonderful Taxonomy Manager module. I don't start a big project without it these days:


  This module provides a powerful interface for managing taxonomies. A vocabulary gets displayed in a dynamic tree view, where parent terms can be expanded to list their nested child terms or can be collapsed.


It's packed with features, there's a list of them on the module page. I think this one in particular will be of interest to you:


  Double Tree interface for moving terms in hierarchies, adding new translations and switching terms between different vocabularies