Should've been more like this

Have Lars and the Norwegian pilot, who doesn't just conveniently show up at the end, come to the conclusion that while they are sure that at least the 2 of them are still human they need to kill everyone else regardless. With these 2 hunting you down, mixed with the threat of the Thing being amongst the hunted would make for some serious levels of paranoia. That would sum up why Colin offs himself so grotesquely. His choices are death by fire or gruesome assimilation. I'd picture it ending coming down to 3 survivors. Lars, the pilot, and a third character who we have been assuming is the protagonist at this point. Lars and his pal confront the 3rd person and he pleads for his life, even cries a little. Completely human. Up until the point where they torch him and dowse him in kerosene. At which point the thing emerges from within, trying desperately to separate itself from the burning flesh of the person it assimilated so well that it nearly believed its own ruse, thus creating split face. I've never imagined split face as two bodies merging together. It always seemed to me like the Thing was trying to escape from itself as its assimilated body burns. From there the dog emerges and they go after it.