I'm firmly in the 'play NRL players in their natural position' camp, and gap fill with NSW Cup players.
Minimal disruption is the name of the game.
Having said that, Salmon did a good job last year playing 6, and if they're worried about Fall's defence - I'd be happy with 7 Cogger, 6 Salmon. Especially so if Tago is back from injury, you could run Peachey at 17.
Salmon is clearly our Mr Fix It option from the bench. He primarily plays back row for us because we haven't had too many injuries mid-game to outside backs or halves. But giving him a few games in the halves during this period keeps his skills up in real game scenarios, and is good insurance if the unthinkable happens later in the year.