I'm not exactly a curateur extraordinaire (I know it's probably not how you say it in French... it should be, though)

In as much as the word "curator" that we are using here does not have the usual meaning (1. A person who manages, administers or organizes a collection or 2. One appointed to act as guardian of the estate of a person), there is no reason to not use the word curateur with a new meaning in French.

So curateur extraordinaire or extraordinaire curateur seems very good to me.