I wish there was a mechanic, where an imitation player could directly infect another player stealthily. If you go out on a mission with someone who is infected, and the mission is sabotaged, there should be a chance that one of those players on the sabotaged mission may become infected.
I think this is close to the mechanic that is being used in Who Goes There? Another Thing game based on the original material instead of the movie. It was on Kickstarter a few months ago. Looking forward to trying both systems out and comparing them.