Inserting a tiny camera into urehtra / vagina. Let it travel up to and beyond the cervix or deep inside the bladder.

It would make for a nice piece of equpiment to have a monitor that needs to be purchased for such tools

One of the things I was disappointed with in the first Rack was the lack of titfucking. I mean where the subject would be straddled.

like cock growth or muscle growth already suggested. test subject grow larger overall

sex organs throbbing to pulse rate, hyper throbbing with a hyper pulse rate

Maybe some of the test subjects require you to use a condom... Or maybe sometimes cumming in condoms is just plain HOT. These things could be either crafted or ordered in bulk.

Make it possible for characters of any gender to have multiple orgasms (orgasms within rapid succession of each other, one after another, for as many times as you want the character to) and long orgasms as well (10 seconds+), where the character squirms in pleasure

Though it can be highlighted and was in the previous incarnations of the games before this masterpiece. It'll be great to see hindpaw/feetpaw play and torture

following options for play?

Digit/toe sucking

licking

nuzzling

massaging

tickling

Also be nice to see a f**ke silly expression for overstimulated subjects that have been mind broken.

An option to artificially induce lactation (maybe through chemical research) or subjects can randomly start with it naturally occurring? Could leak while playing with their breasts, and potentially spray while they orgasm.

Might tie into breast expansion as the milk causes their breasts to enlarge.

Use fingers or toys (by hand) in order to milk a male via prostate. Preferably into an open container, but the container is optional.