I dunno, acrediblesource. I think the sight of Alien's jizzing cocoon material all over everyone might be a bit too comical.
I was leaning towards the "it would've been unintentionally funny" angle...
and then i remembered that there's a moment in It Follows
where the lead character glimpses the "creature" forcing itself
upon the corpse of a friend.
And it's horrifying and uncomfortable...
There's also a similarly uncomfortable scene in Possession (starring Sam Neill).
Bottom line - The effectiveness of the "cocoon" idea depends on the writing, filmmaking, etc...
But i actually think it could be used "well"... there IS precedent.
I wouldnt trust Ridley with it, though.
Maybe David Robert Mitchell.