Ideas
+216
Standing/Obedient Test Subjects
Test Subjects that you can sex without having machines holding them, the players can fuck them in a few different positions (ex: bent over, standing, agaisnt wall, etc.) and the Test Subjects can also fuck the player as well if they have a penis.
Wether it's the player fucking the Test Subject or the Test Subject fucking the player, both ways could count with the same positions.
Customer support service by UserEcho
You could put in different types of stations for something like that. Like instead of the titular Rack you could have a simple doctors examination table that has different effects on the interactions you have. Perhaps even limiting some interactions to one set up or the other. Possibly make it so the unrestrained subject will work themselves to provide samples but obviously without the control or quantity you would get otherwise.