I believe Elliot can play 13 or fill in at hooker. Crossland does work hard but he doesn't offer anything from hooker. If he isn't going to offer anything, I'd rather rest Brailey 10 minutes a game and have Elliot fill in.
Start with 9. Brailey and 13. Gamble and then bring on Elliot for Gamble first, being Gamble back on and give Brailey a short rest and then Elliot can go off for Brailey again.
Mann can be 18th man. I want Crossland to succeed but he really isn't good enough for a team trying to make the 8. Crossland has played 10 more NRL games than Gamble. One looks like he belongs while one still fumbles around.