For Willie to play OL in the NFL its going to take him years and years of practice and experience not in the NFL, either CFL or NFLE. Even in those leagues, theres Ex D1 players, so chances of him getting that experience are extremely thin. We can there for rule out OL.
FB is a possibility. He would have to learn how to block but I think he can do that in a year or two. Biggest issue here would be the craziness needed to play FB and be able to hit guys that are 6'3, 240 ripped, and run 4.6 40's, meet those guys head on and drive them backwards. Football is more violent out there on the field than most Australians can imagine.
DE is a possibility but again like OL he is going to need a lot of training and experience at it to make a go of it in the NFL. The offensive tackles out there are already experienced in blocking against Defensive End's much faster and agile than Wille. So I think if Willie were to be a DE, he would have to be a back up / special teamer.
LB I dont think is so much of a possibility. Again he would need to get faster and agile, and crazy.
TE, now here is where he could have a shot. If hes a smart guy it could take him only a year or two to work on his route running technique and reading coverages. Blocking im sure he could get by on TE standards with a lot of hard work. The main problem here would likely be catching the ball. Catching the ball with a LB ready to smack you into yesterday, not to mention the speed and velocity that NFL QB's throw with. It would be very very tough adjusting to all that and would take him some time. But if theres any position he could make an NFL squad on, this would be it IMO. Someone said Antonio Gates did it, but this guy is an incredible athlete for his size and strength. He is so agile and has amazing hands and he wasnt a star right away, it took him a year as a back up and im sure a lot of extra hours training.
I dont know if I would buy into the Islander bloodline sort of thinking. Here at my college we have quite a few big Samoans, and these guys are beasts, they are good good players, roughly Willie's size, just a little shorter and this is one of the lowest levels of College Football! There are so hundreds of College Football Teams. One of those guys Samoan brothers has a shot at the NFL but he is 6'4, 340 Defensive Tackle.
I hope Willie gives it a go and reports back on how he does training with an NFL team. Willie would have to give up Rugby League Fame for at least a full year or two of learning how to play whatever position he chooses, and then hope that he is a freak of nature and can be an NFL player. Lets remember Paul Sironen decided against continuing at the University of Hawaii after one year I believe and then came back to Australia to be a league legend. Maybe Willie can report back and give some more credibility to the incredibly complete and violent athletes the NFL has. I hope he makes it, like I mentioned above, I think TE is his best shot!