He could go to Canberra. Imagine if they sign Williams from Wigan and Thompson from Saints. 6 Englishmen in that side!.
I agree not all NRL moves are great ones and given the evidence it seems for a Back it will be hard to make it down under (Tomkins, Eden, Sarginson, Turner all struggled to varying degrees) , Even the very good Ryan Hall is going to find it tough once fit to break Into the Roosters backline.
For Forwards I would say there's at least 20 SL English players who would all be good NRL Forwards and another 20 English and a Frenchman or 2 who would cut it as First 25 squad men.
With Backs, Williams, Fages, Ratchford, Lomax and a Fit TJ stand out as Backs who would make a impact out there. Pace and the ability to change direction at pace is a massive thing for Backs in the NRL.
Thompson would do well, however I agree Saints is a very good place to be and it would have to be the right move for him to a club that offers something career wise that is a step up. Saints have got a very strong team now.