not a teacher
The term "fox heaven" refers to the "fox" type of personality as described by the philosopher Isaiah Berlin, which is mentioned earlier in your quote. If you go to this Wikipedia link, under "Summary" there is an explanation of the term:
The Hedgehog and the Fox - Wikipedia, the free encyclopedia
So, here, the health care bill was the sort of lengthy, highly detailed document that the writer feels was typical of a "fox" personality such as Clinton. The suggestion is that Clinton would have greatly enjoyed being involved in putting the bill together – it was "fox heaven".