While the goo certainly changes some zombies to an extraordinary extend, i don’t feel like he would…basically destroy the human body in favour of, well, tentacles. All the zombies, as far as I remember, kept their overall appearance, with some minor adjustments, like stretched arms/legs or a bloated body of some kind. Well, at least I can’t remember a Zombie which wouldn’t fall into this category.
What you describe sounds more like a Nether-Creature ; or at least one of those earth-horrors, like the Amigara, the Thing or human snails. And those usually don’t use CBMs - i actually doubt cbms could work on those creatures, as their DNA and overall biological and chemical makeup seems extremely different to that of a human, which the cbms were made for.
Also, why going so far as to make a tentacle monster? Do you happen to have an Anime Character / Otaku as Character? Oh, you so kinky. cough cough
Jokes aside, we have to consider the following:
Why would a zombie have an Artificial Night Generator? Or more exact: Why would the Person who became the zombie have this CBM? As it stands, i don’t really feel like a 0815 human would have something like this. A CBM which generates dark night around you sounds more like something for a military operator, or some kind of spy or assassin. So, why not make something around that Idea. We already have zombie soldiers and zombie bio-operators, so one could easily make a variation of those and call it Zombie Assassin, something like…
Barely visible in the Darkness around it is a figure clad in what seems to be a dark, military uniform. It’s eyes glow red, the only light inside this Sphere of utter blackness. It seems to be an augmented Soldier, maybe once part of a Special Forces group, specialized in Assassination. Whatever may be the case, its motions are smooth, its eyes looking for prey. Do you really want to fight it?