I've seen him play a countless times including a few in person. He is incredibly talented rugby league player and obviously its a completely different game but I think he has the skills to be a really good special teams player. Rugby league is known for its tackling and that combined with his speed I could see him being a gunner and also a returner.
I cant imagine Hayne actually playing running back in the game because that is too drastic of a change but yeah definitely has the potential to make a difference on special teams as his position in Rugby League is very high pressure and always dealing with high kicks, returns and try (touchdown) saving tackles... Good on him for trying though. The NFL is really popular in Australia and this will only increase peoples interest so its good for the game. Also just to explain as its confusing, Hayne played Rugby League which is a different sport to Rugby Union which is mainly called Rugby. The rugby world cup is whats happening in London during the Bills game there this year and that is not the sport he played.