a sound is a medical device that is inserted into the urethra to expand its diameter they are usually metallic rods

Tentacle clothing / living clothing is kind of like a Zero suit / latex suit but it's alive and can apply to male and females. Kinda hard to explain but you can look up hentai of it for a better understanding. 

Mummification is obvious. Mummification with latex and other materials while also being able to toy them. Also you could put them inside a mummy box with vibrators and such, which could also account for sensory deprivation.

Aliens / parasites could be good for egg laying and also some could be used on male subjects if the alien / parasite / creature is penetrable.

These are some kind of specific suggestions and fetishes but I wanna know what you think.

Perhaps also canes and switches for a bit of rougher play

I wish you could walk your test subject around a room with objects in it to make it wiggle on the inside and once the subject is well aroused and read, you can lock him in place on 4 paw position to fuck tail up face down, and maybe a 3 some function could be a fun addition.

If you grow your persons balls/breasts/udder so much (and item that lets you increase production of cum/milk) they will break the chair. but will still not be able to move there hands or feet since they are strapped so you have hyper goodness :D they need some milking and some fucking in order to re leave that presser :D they would then be supper sensitive :D (maybe sell the contents to make money :D) also this would be same if hyper pregnant with live or eggs they look ready to burst... but they wont they just look like it and they grow if not birthed :D

This would be nice

I really would like to see this 4 devices in game they don't need any special utility but for example ring gag could later in development help with possible oral activity

using vaginal and anal speculum could be added visible contractions during orgasm or pain

and x-ray could be in form of glasses or tablet like device that allows you to see whats happening inside.

What about force the subjects to do some physical exercise like tied up on a treadmill leashed on the neck or balls or work with weights with butt-plug "punishments"

To put go fuck yourself on a whole other level.