I think Leilua has been far and away the best centre in the NRL and should be the first player picked for NSW.
Also J. Trbojevic is the best defensive middle forward in the game and would be my first forward picked. I think he is the perfect 13. Would prefer Merrin to come off the bench as his greatest strength is the havoc he can cause in the middle with his footwork and offloads.
The hardest position to pick is left centre/wing, on form Latrell Mitchell has looked far and away the best in attack, but he has shown some defensive lapses. With Boyd Cordner a definite for left edge forward, if Mitch Pearce is picked at halfback you might as well pick the entire roosters left side.
I think the most talented hooker for NSW is Damien Cook but he hasn't had enough game time coming off the bench to show what he is fully capable of. I'd see how he handles starting at hooker over the next month and choose between him and Wallace.