What about this format:
The story starts with an ad posted on Craigslist by a "scientist"
"Seeking paid volunteers for science experiments. Safety not guaranteed"
(Basically)
The story is told 1st person from a volunteers perspective.
"I am a part-time Barista at Starbucks. I've answered ads on Craigslist before. One guy wanted me to kick him in the balls for 20 bucks. I had to clean up some smelly apartment for 100. It was never pleasant but I needed a side hustle and I didn't own a car to drive for Uber"
Basically, a millennial maybe with low self-esteem/self-worth who is down for whatever.
Then they describe the scenario:
There were six men, and six women. He offered us laughing gas and I was like "Cool, we are doing drug testing! What other drugs do you want me to test?"
She wakes up with a giant penis. The men subjects all have pussies.
Then she has to go about her life that way.
The next chapter is a different subject. He elongates her tits and compresses them so that they hang down to her waist. He reshapes her ass so that it becomes much plumper and inserts a permanent tube in her asshole so that it never closes. He plumps out her lips and makes them look like a labia.
She is the bridesmaid in a wedding and has to go to the bachelorette party.
Each science experiment is weirder than the last. Sometimes he creates a new life, sometimes he creates a sexual abomination.