A model like that might work, but the issue there is twofold. One is that because of the funding structure, they are always beholden to a third party. It doesn't really matter what organization you work for; you always know where your money is coming from and you make sure you don't piss those people off. If their money was solid and secure, then they'd have independence in that sense.
An example is the U.S. Energy Information Administration. They were created in the 1970s, and various parties have taken a run at them, both in terms of the legislation but also their budgets, and have been unsuccessful in attacking them. You can get at an organization through its funding, so that is one aspect.
The other aspect is the secretariat function, because the secretariat function can be staffed by someone else, and they'll staff it with the kind of people they want to have to make sure that whatever they're looking for from that organization is going to come out of that organization. I'm not saying that happens, but there's the opportunity for that to happen.
If there's an opportunity for that to happen, then other people would look at that and say they have a credibility issue. They have a credibility issue in terms of the budget as well as the staffing.