Alien Fun For A Few Sessions
This would be fun for a one-off, or a game that lasts a couple of sessions. It's the traditional Alien scenario. It would take little prep by the GM.
First, tell your players you're playing Traveller. Don't mention Alien.
Second, grab Broadsword. You've got a big ship, and you've got every PC detailed for you. The players will play ALL of them (many of them won't be lasting, anyway). Just divide up the entire crew of the Broadsword by the number of players you have--allow them to play multiple characters.
Third, grab the JTAS article that covers the Alien.
Fourth, begin the game like a normal Traveller scenario, with the players playing the crew of a Broadsword class mercenary crusier. Then, allow them to jump into J-Space.
Now, you have a week to kill 'em all!
The alien is hiding, of course, on the ship. You might want to start some scenes by randomly killing some NPCs without letting the players play the characters. The crew is just missing....in J-Space. The ship is big, but it ain't that big.
Watch what the players do. This could be fun...they don't know yet that they're playing a traditional Alien scenario.
And, once they find out, it will be, "Oh, Crap! What's that sticky stuff!!"
Then, start whacking the the crew with the Alien hide-hit-and-run tactics.
If the Broadsword isn't big enough, then bring out your Kinuiir deckplans...or even your Azhanti High Lightning. Annic Nova, maybe. Under this scenario, you don't have J-Space to isolate the PCs (but, you're in space, so it doesn't matter). The Broadsword finds some wreckage, a dead ship, hears a distress signal...whatever.
Now you've got plenty of crew to eat up (the Broadsword crewmembers), and you've got a big map to hunt around in.
Maybe throw a twist on the old theme? Remember, the Aliens communicate telepathically. What if you have a psion aboard? What if its an Imperial crew, and the psion was hiding his ability?
That could be an interesting dynamic.
Another aspect to this game that will be fun is seeing who will survive! Like I said, just divide the entire crew of the Broadsword up by the number of players you have. Don't play favorites with the captain or special NPCs. Just see where the scenario and the dice take you. The GM doesn't know who will surivive and neither do the players. It could be the Vargr second APC gunner, for all you know.
Heck, this could be a cool basis for a beginning adventure of a campaign. Whoever survives will probably be tight with the other survivors.
Sounds like a fun scenario, eh?