I think that in the first meeting between Grace and Simon, Grace should be allowed to bite and fight dirty.
I know that Simon would win a fight against Grace, they are made different and all that. However, it seems that when they meet Simon always goes ready to kill (which is justificable given his past), and Grace just there been like "Hello I'm Ryland Grace..." and PUM! Simon is over him ready to suffocate him and Grace is like fighting to breath, but never hurting Simon, just struggling against him, and the fight ends usually by: 1) Simon is able to heard reasons and gives Grace a chance but is very suspicious of him, 2) he just passes out, because pain and exhaustation would do that to your body, or 3) (and the funniest one to me) Rocky appears (like the saviour he is) and knocks Simon out.
I would want to introduce the idea of Grace fighting back.
Grace may seem like a stable person at first in comparison to his companions; an alien who had live in solitude so long that has separation issues, and Simon who is his whole case of study with mentions of cults, facing god and been a child soldier. However, Grace is an anxiety bomb, who has a bad history with people, I think that if Simon just jumps over him, Grace would fight like a mad man.
It doesn't matter which Grace you know or like the most (personally my mind have just make an amalgam of the book and the movie) he would have the motivation to fight; Book!Grace, who was drug in the spot and sent to a cell to wait to be sent to die would fight now that he can, because he knows what kind of stuff happens if he doesn't react fast enough; Movie!Grace is a person who panics, but after a moment of shock he reacts as we saw in the movie doing his best attempt to dodge guards and ran as fast as he could. Besides, Grace wants to live, that is the origin of his determination to get through things, so if he thinks that Simon is going to kill him he would fight.
Of course, he can't win, and he knows he can't win, but he would try, bitting and scratching, kicking and squirming. Let him play dirty; If Simon's amputation is fresh, let Grace prick the exposed nerve; if Simon has raw, sensible skin from the mutation, let Grace scratch there; If Simon is close enough, let Grace poke his eyes.
He can ask for forgiveness later, when he is back to be Grace, right now he is just a scare man who wants to survive.
