Idris has been regularly racking up 150m and getting through quite a bit of defensive work. He doesn't really get much fitter. Only thing holding him back is having to do that work. Its impacting his effectiveness running wide at speed and creating problems for smaller backs. That's a club issue though with Penrith props not getting enough go forward.
I'd go
Hayne, Morris, Jennings, Morris, Hoppa, Reynolds, Mullen, Woods, Farah, Gallen, Graham, Sims, Merrin, Watmough, Lewis, Tamou, Williams
I like that side but I'd pick Lewis and t-rex to start and then bring on Graham (for t-rex) and Watmough (for merrin) with Lewis playing close to 80 on the right. I would also have Mannah on the bench. BTW both sims and Merrin are middle forwards predominantly, who are you shifting to the right edge?