ehhh the neomorph like "new beast" was very specifically the product of experimentation.
the actual alien itself was still of the "egg, facehugger, chestburster" variety. And was still stronger than the new beasts.
I liked how Gibson defined the alien genetic material as being almost like a nanomachine, with some limited adaptive abilities that allowed it to gain a new form. I got the impression that gibson wanted to imply a low level of artificial intelligence in the thing... and it probably became the "new beast" as a last resort thing. Maybe the "new beast" would end up eggmorphing people and that would then bring about the old regular "perfect organism".
I was kinda ok with it. Lots of ways to "fanwank it" into making some sort of sense.
Best of the abandoned scripts at any rate.