Why collaborate? Collaborators make life difficult, can steal your work, and wouldn't you rather have the glory and be your own boss? Yes, you would :)
The purpose of a review is not to improve your network. It is to increase your academic standing. I can assure you collaboration is not the way to go and in fact is unnecessary in the writing of a review paper. No one will do it anyway. Once published, the review will improve your networking. I personally will never collaborate :)