What about something where the BE is implied. I mean, not a direct statement in the storyline, but something that is constantly taking place throughout the story that no one addresses directly. For example, maybe there are a few characters who keep getting bigger throughout the movie - sort of the way that Igor's hump in Young Frankenstein kept switching sides. I was watching this movie called Ganja & Hess (it is a great film starring Duane Reed and Marlene Clarke - you should see it if you haven't already), and the director was talking about how everything that happens in a film doesn't need to be explained or even have to make sense. In that way, it requires the audience to invest some mental collateral to connect the dots.
As far as a plot - maybe this isn't so much a Sci-Fi idea, but there is a movie called "The Beast Must Die" where a bunch of guests are invited to spend a weekend with a host who is convinced that one of them is a werewolf. The movie works by writing in the tension more so than actually displaying anything really fancy. It's kind of low budget (there are no transformation scenes and the actual "werewolf" isn't much more than a giant dog), but the directing and the script make for an interesting watch.
Perhaps there is something in this you could use. Maybe a group of space colony pioneers trapped as a result of the political violence that has erupted on their planet. Maybe this takes place in a future where body modification is so normal that everyone has an enhancement of some type (this way you escape the obligation for nudity or explicit sexual tones). Maybe it is sort of a mix between "Saw" and "Total Recall," where the trauma of the situation has caused some memory loss, and all of the people are trying to figure out which one of them is responsible for the attack that has them trapped, and how are they going to get to the manual override system to turn the air back on before they lose their 48 hour supply of oxygen (so you can do that "heavy breathing" that people like so much).
Just a few ideas… let me know what you think.
Yours truly,
Rbix