She wants to be in your Harem

"I-I want... to be in your Harem!" Amanda blurts out.

"I don't have one?" you ask confused as you gently run your fingers through Gwen's hair. "but I wouldn't be opposed to having one."

Amanda's eyes lit up. "you mean it?!"

"of course I do." you answer.

"thank you John! Thank you!" she basically squeals in excitement as her glasses almost fall off.

"now, how will people become part of my 'harem'?" you ask.

"A-already thought of." Amanda says as she materializes a collar out of thin air. "just place this around their neck and they'll be yours!"

you take the collar and look at it closely, it's a fairly basic black leather collar with a metal buckle. you ask Gwen to stand up which she obliges, pulling off your cock with a wet pop before kissing the tip and standing up. once she's fully stood up, you reach up and wrap the collar around her neck before latching it shut. the moment you take your hands off Gwen, a faint glow comes from the collar as Gwen's pupils become hearts. a small barcode tattoo appears on her left breast.

once the glow recedes, you notice that Gwen isn't moving. you try touching her, getting no response.

"scan the barcode." Amanda suggests with an awkward smile.

you pull out your phone and scan the barcode, opening an app that showed a 3d model of Gwen with the words 'click here to claim.' as you click it, a new tattoo appears on Gwen's right breast reading, 'property of John Doe.' looking back to the app, you notice some new stuff has appeared under the model of Gwen like her stats, some basic info, and a perk tree?

"so, u-uhm. I thought making it like a game would be more fun for you." Amanda explains, trying to sound innocent.

you look at the perk tree, Gwen is currently level one and has no class picked, but has the option of doll, cow or succubus with multiclassing options at a higher level. you take a look at the description of each class.
doll: as her level increases, she'll turn more and more into a living plastic sex doll
cow: as her level increases, her breasts will develop and she'll start producing milk
Succubus: as her level increases, she turn more and more into a submissive succubus

you take another look at Gwen's motionless body as class continues in the background, ignorant of what's happening as Ms. Harkness flaunts her body casually like it's a regular Tuesday.

looking back to your phone, you make your choice...

(feel free to submit ideas, and even character to add to the Harem)