have a multiplayer server feature so when u play can have more then one person on one test subject. or have a massive multiplayer server so other people can show off their character socialize and even interact with each other like u interact with the test subjects.

A room where possible test subjects are waiting.

Maybe with some time constrained mini game.

While you are doing research or tending to a test subject, the comm system announces:

"Dr. Fek (or insert players name here) please come to the reception area. Dr. Fek please come to the reception area." And you have one minute left to get dressed and fetch the WELL paying customer. If you come to late, the customer is gone, and the bonus money is lost.

cus sometimes you just REALLY like the character that you made, y'know?

Erection of the character's penis (or swelling of the vagina) while he/she masturbates experimental customers, or in any other way to satisfy them.

I'll add a image later lol

Always been a fan of Heterochromia. It could be linked to the "Unusual fur colors etc." thing for the test subjects.

horizontal rectangular pupils - goats and other bovidae animals

vertical slit pupils - cats/reptiles

The ability to have sex with either favourated test subjects / clients / research subjects or coworkers outside the work enviroment purely for the characters' recreational purposes, perhaps even with dates paths (?)