Well, they cut the Kettlebacks, that's the problem (of arresting Margaery). I think it was probably a good decision to cut them for the television show, but Cersei really needs some figure to be her man-pawn in KL - you have the disgraced Maester doing his Frankenstein thing in the basement, but that's it. Trant could have admirably taken that role, but apparently Trant needs to be killed by Arya.
Without that henchman, the whole plot against Margaery is nothing but the verbal sparring we've seen between the two. I don't recall exactly why Cersei wanted to arm the Faith Militant in the books, but it wasn't to get out of her marriage to Loras, she did that by asking him to storm Dragonstone. Was it solely to plot against Margaery? I don't even remember any more.