How have any of those guys redifined the position they play in?
Lockyer redifined the fullback role, turning it into a second 5/8 so to speak. Slater's ball playing skills aren't/weren't in the same ballpark as Lockyer's. Slater is very quick and elusive (traits that have existed in fullbacks for years) but his ball playing has never been brilliant, and his kicking game is non-existent. Top player for sure. Redefined fullback? No way.
Cronk, Thurston, great players. But what have they brought to the Halfback position that wasn't already there? Competitiveness on Thurston's part I guess.
Smith's a genius, but again, outside of his gamesmanship, how has he redefined the 9 position? I don't count wrestling, whinging and smugness as positives. He's the only one in your list I'd make an Immortal, even though the concept is silly.
I'm not criticising your choice of future immortals, but you're criteria is very questionable.