As for this "Gambit never kills" thing... who came up with that? I never did. But I can assure you, unlike Wolverine, I can recall every time he has on panel. Gambit can kill to defend his life or those around him, but he's not a killer. If any of you think otherwise, you never understood his character. He's more than his powers and shouldn't be defined by them. His powers are actually the opposite of who he is. They are brash, loud, and flashy. Gambit is smooth, charming and stealthy. It gives him depth. In a way you can say he doesnt even want his powers, at least not in the way most think. He tried to have them watered down and when he lost them after XXM, he didnt go on any journey to get them back. I can argue he adjusted and didnt really want them back all that much.
My outlook... If Gambit is going to be rated R for anything, it should be other things rather than violence. It's a new era Fox X-Men franchise, following Deadpool and Logan, it'd be expected. An R rating IMO should be because of content such as sexual situations. Now because that can easily push it up to PG-13 alone, they have room to tip it over by using language and THEN they can go over the top with a few scenes of graphic violence. But if anyone thinks it should get an R rating just due to his powers, then your asking for a movie that may not represent the Gambit you and I know, and most certainly not the one Fox, or Tatum want. It doesnt need to be Deadpool. If I'm looking at this right, they will use this as much a genre flick as they others. They got a Western in Logan, the action-comedy in Deadpool; Gambit is probably going to be something all its own. Most likely an action-thriller with healthy helpings of romance. It may even be a "caper" like the Thomas Crown Affair (but not nearly as stuffy, the main character makes things blow up lol) or crime-action-drama (again, not as serious though, still dealing with Channing Tatum here).