I'll just chime in briefly by saying that I think you've put your finger on many of the deep structural problems of the United Nations. These are not simply those having to do with some of the administrative constraints that were outlined in the Banbury op-ed, such as the difficulty of posting people to field missions and having them work under the guidance of other departments as a result of the inability to harmonize the conditions of service amongst people working in two different UN agencies.
The difficulty of untangling those administrative knots is something I don't know the details of, but at root it would seem to be a difficulty that many of the reforms that are being driven to try to make that system more streamlined seem to be coming from some of the countries that are already seen to have disproportionate influence over the United Nations through their funding, etc. That tends to kick-start an automatic reaction from other groups of countries who feel that any such reform is clearly being done to further heighten the power of certain groups in the United Nations. Then you end up with a standoff.
Some people have argued that until the basic political settlement around the Security Council's permanent membership is figured out, it will be impossible to take all the necessary steps, some of them obvious and some of them non-obvious to those of us who are from the outside. It's certainly the case that the more one layers within institutions—let's say specifically the peace and security sector, such as the creation of the UN Peacebuilding Commission, the UN Peacebuilding Fund, and the UN Peacebuilding Support Office back in 2005—the institutions aren't leading to the coordination of work in other parts of the UN system. They're just adding new voices around the table, which has grown increasingly cacophonous.
That's not always the case, but it's frequently the case. Canada has been a member of the UN Peacebuilding Commission and has done great work there, but I'm sure those who've engaged with it on a day-to-day basis would have the same feeling, that there needs to be a streamlining rather than a layering of additional reform elements, because that's what UN reform tends to be—new layers, more difficulties.