First off, I think that vehicles and Items are the two things always needed in The Thing, so they will obviously be needed in The Thing 2! Also, not seeing other players is needed! That way everytime you meet someone you get scared. Third (I think), you need to make everyone the same color. Last, having a good engine for body tempurature and a random decision for picking who is the thing should be in.
Whatever you do, try to avoid the mistakes made in The Thing Ice! It had a story, but the story was stupid, you find a dead body and then BAM, someone is the thing. Then you have to find these damn crystals. What the Hell is a crystal going to do, and why are crystals buried in Antarctica?
As far as story goes, just do something like a ship crashes and people are stranded with just a few weapons, or better yet, no weapons. make it so people have to find what weapon they want, and then go with that! Also, put in a nice twist! Something no newby to the game would ever expect, like if you have them radio to get out, make it that the first ship crashes and they have to send another, lengthening the time of gameplay (that would make a newbs mouth drop

)!
That's about all I have to say, but finding weapons instead of just starting with them would make a nice touch if you ask me, unless it is a military ship!