The trainer being an ex has certainly worked with other clubs, Sutton at Souths, Ryan Hoffman at the Storm, Peter Wallace did it at Penrith, Alfie Langer etc. Ronnie Palmer had his last 1st grade game 26 years ago, maybe his knees are shot.
I don't think Farah would be afraid to speak his mind, I think it would work with the likes of Adam Douhei and young Simpkins, Farah apparently was working with the 9's over the summer.
Brooks on the other hand, well Brooks always looks intimidated by Farah and Marshall so if Farah was going to get up him, I think Brooks will not just get back in his shell, he'll stay there.
I wonder though if Madden would see Farah on the field as a bonus, perhaps he enjoyed working with Farah over the summer alongside Simpkins.