GURPS Monster Hunters is one of my favorite gaming series of all time - and not just because I got to playtest or have wrote a bunch about it - I genuinely love the premise. I've always been partial to the horror genre, especially the kind where the protagonist knock some heads. I still regret not being able to playtest GURPS Horror when given the chance, but cie la vie. A while back someone asked me to discuss the Experiment template from Monster Hunters (I've been steadily chewing through requests, so if we haven't gotten to yours I will - just give me some time). The "Protean Man" is a another concept I'm fond of and given my background with such games as Nightbane, Beyond the Supernatural, and World of Darkness I'm quite familiar with its use. Body horror is one of those subjects that folks usually either love or go squickity-squick... I'm one of those weird people who are somewhere in the middle. For example, I love John Carpenter's The Thing, but have issues reading Scott Sigler his work however brilliant it might be.
The Experiment from Monster Hunters occupies some of the in-game themes and out-game roles that the Inhuman does (otherness, non-humanity, etc.), but in a different way. Whereas the Inhuman is a product of the setting's paranormal laws, the Experiment is the product of man. Specifically, the product of man thinking that he is God. Despite Monster Hunters' fairly light tone overall...this does bring a certain dramatic weight to the role. A Inhuman vampire might be trying to redeem himself for his past sins and may very well not be responsible for his current plight...but the Experiment is literally sin embodied. He is hubris given form in the most literal context. He might not have asked for what happened to him (and it can be argued that neither did the theoretical vampire), but he is another man's ego in the flesh. Just think about that for a minute. His inhumanity is not the result of a attack by a fellow monster or some curse or accident of birth: his was planned and executed by someone who thought they could do better than God, Mother Nature, evolution, etc. That lends some gravitas to the role that you might not find anywhere else.
Now, on a more game-mechanistic side of things, you could do a lot with the Experiment template. For example, psionics might not be naturally occurring. They could be due to a vampiric breeding program to make humans more subservient to their own mind control powers, except that one out of a thousand resulted in a human who was a little bit psychic. Before the vampires knew what they had done they'd accidentally bred psionic powers into the human population. You could do this with any number of paranormal abilities. To create such a character, the following lens might be useful:
Advantages: Exchange Bioenhancement Talent for Parapsychologist 2. • Pick 60 points worth of Psionic Talents or Abilities instead of Bioenhancement powers. • Add both Bioenhancement Talent and Bioenhancement Abilities to the second choice list as optional traits.
Picking Over the Bones