A single slave in the facility is singled out and permitted to cum while all the other slaves are in complete orgasm denial. If s/he has been selected previously, the slave begs and pleads to not be chosen again. The chosen slave is fucked by machines, the PC, or someone else, or all of the above until they are sick of orgasms. An alternate choice is to have the denied slaves service the chosen one (PRAISE BE), which would build resentment. If the PC is feeling generous, they can elect to release the pent up slaves to gang-fuck the "lucky" one (re:bukkake). Alternatively, the PC can instead have a marathon of a session with the lucky one in the center of the facility while the others watch. Could go any which way, really. It's all about the haves and have-nots

i would like to preform a certain combination of actions on the subject. Like to be able to use a dildo on the subject and at the same time give him a blowjob. Or fucking the subject and jerking him off at the same time. Or riding him and having my character jerk himself off, combinations like that.

It may be cool to not let what we gather go to waste, after all

Thrusting into the subject's mouth could be fun!

See below:

Press 2 or 3 during while using the mouth tool to sniff or huff selected body parts.

Pros: Can be used to add buffs to player's cum volume cum spurt strength and frequency, stamina, orgasm duration, reduce refractory duration, and increase subject anticipating.

Cons: Excessive huffing may cause player to pass out from lack of oxygen.

Note: Sniffing is just smelling a body part up close, while huffing is when you cup your hands around it or bury your muzzle in to a body part.

Personally, I'm not a fan of visible nipples on furries. I get why they might be wanted here simply because it's an extra spot that people could interact with who are interested, but having the option to remove them from custom characters would be awesome.
In my opinion, nipples should hardly be visible if at all simply because they are covered in fur. But that's just me being picky. Currently I try to mask them with same color as the fur around them.

Currently when using the dildo it performs an action but is immediately removed when player interaction ends. This proposes the idea that (like in the first Rack game) where applicable toys/objects/tools could be left 'equipped' to a subject. This would move the object from the toolbar to the test subject's equipment slot (which must be free for the action to be allowed anyway, if I understand how things work currently). If the object is not at a sufficient status to be left, it could return to the player's toolbar as is the case (for example if a dildo was too far out to stay without falling out).

For example, the dildo could be left within a subject at its current depth. Another example would be a 'fleshlight'-like sleeve. Such objects would be able to be equipped from the inventory screen for an NPC or player as well. This would allow for example the player to walk around with an inserted toy/object as currently works for cock rings, but would apply to applicable interaction objects as well.

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.

pingpong balls, stick, food, etc