I. e. a knotted cock will get stuck in a hole when sufficiently excited and inserted deep enough.

Staying there unless forcefully removed with a sharp tug, expelled by a very unhappy partner, or the excitement level falls low enough that the knotted cock can freely slip out.

A tied knot should give (extra?) stimulation when tugged outward (but not free), and possibly act as a hindrance (but not completely, if implemented) to cum spray.

Basically just making the subjects' belly bulge after they've been filled enough, and maybe make the cum start coming out of the other end if they're full and are still being filled.

You know that portrait system for when characters talk? Let's use that and make it so that it can display X-Ray views during sex as well.

To be technical, this would not just by the current camera that is just zoomed in too close. It would be showing a "copy" of the player character's/power bottom's penis, one that doesn't contort or warp to prevent clipping issues while it's being smothered by the retriever's insides.

For said insides, I'm thinking we'll have to be creative. A combination and 2d dynamic pulsating overlays along with 3D models that have internal detailed textures but completely invisible external textures, to allow for free moving camera that's not stuck to just one angle.

And of course, this could be used to show the cream pie flooding of vaginas, mouths, wombs, throats, intestines, etc, etc.

Penetrate test subject with Penis and Dildo, multiple dildos or Penises (Portals?)

Double anal / vaginal or anal+vaginal

Love the cock milking but would also love to see some breast milking as well!

Penetrate the Sheath or Slit of a male with a Penis or Dildo.

The ability to inhibit orgasm through various devices, chastity cage, chastity ball, chastity belt, or even an orgasm inhibiting headband that prevents the pleasure center of the brain from sending the climax signal, to really build up that need.

Cum should leak or even spray out from the stretched walls of a stuffed vagina (tail hole as well?) when it's filled to capacity with cum + cock. Perhaps a displacement of fluids effect due to phallic object entering a hole and pushing the fluids out. (It all has to go somewhere right?!)

If impregnation does get in, then myself would like it to be a fairly big deal. Breeding certain traits, physical or mental, having the PC mate with whomever and be able to knock them up/ be knocked up. And Have it focus on the pregnancy, swelling belly, lactation, peeing more and perhaps strange cravings. Then, after the offspring is born, you can make it grow up quickly somehow, and afterwards, mate it with its mother and or father, to then knock them back up, or be impregnated. Maybe depending on the subject, they could be really against it and you have to force it, or they could be excited by it. And some nice breastfeeding, incestuous or no, would be fantastic. Lactation over all would be great. Naturally or artificially inducing it. However, have an option somewhere that enables hyper lactation with small breasts. Because me, myself and I, vastly prefer little mounds to big boobies. And that's a very sexy thing, getting a lottt of milk from a little tank. To me it is anyway. And of course, this would all be for herms as well. Now, solo watersports, not everyone likes them, and that's fine. But me, I would loovvvve being able to have female/herm subjects pee themselves. Really detailed, watching the urine flow down their fur, soaking whatever it comes into contact with. And making them hold it would also be a big part.