Not sure it's quite that simplistic Richie. I think that either of your Loose Forward or Fullback need to be able to play an extra pivot role. Usually its the Fullback because this means you can go with an extra prop in the 13 jersey, but for me that's probably down to a lack of really good props in SL (Peacock is still considered good enough to Captain England as an example) and also the structure of attack.
Just because Wigan do it with Tomkins, doesn't mean it's compulsary. It's about getting the best out of the players you have on the roster, and giving them a structure that they understand and can implement.