It's not necessarily true that you can't take MK to battlefield, because you can camp very well there because you can make an easy fortress witch claymores/c4 and camp your nades like crazy and if he chooses to fly over your c4 you can use your mortar. The way I feel about battlefield is it's very momentum based, but that's how the MK/Snake matchup is. If you can get them away and setup your traps battlefield is a fine stage, just avoid getting on platforms, and if you do, shield drop a nade, good chance if they're aggressive enough it'll work out in your favor.
And about rainbow cruise, I was going to start a thread about this soon, because I honestly don't see it as a bad Snake stage. Mind you I say this after I got thrashed on it against a DDD, but I made stupid mistakes and such, but I also 3 stocked a very good DK. On RC, as long as you take the defensive side of the map and stay ahead of your opponent, I find it to be a good snake stage. I'm not advocating it against anyone who would definitely do better on it like MK, Rob, or Pikachu. But the low ceiling is useful, and as long as you're staying ahead and keeping defensive sides, you can easily pressure your opponent with your explosives, and when they get close, you have plenty of options, because now you have your back to a blast zone, and throwing someone and reacting properly could net you an early kill. Yes, there is the risk of them grabbing you, but remember they're approaching you, and you just have to read accordingly.