I wish people would read the threads a little more.
It's common sense already they wouldn't have to remain faithful to the size of the thing for MP ... I remember someone mentionning the example of Raam in Gears of War, too. Which was a good example.
They have to keep all the characters the same size for MP, but that doesn't mean they can't use their basic look.
Beside, we already saw a MP Praetorian model, and it was the same size as any common Alien. Why couldn't the Predalien be so too ?
There are even more reasons to believe it's gonna be a MP skin since it's gonna play a part in SP. Mark my words.