"One of your coworkers is wearing one of those 'auto-orgasm' things, and you've got the remote to it. Go figure out who it is." Or, "The custodian has been a jerk to you recently. Portal some vaginas to the showers and make a mess." Or, "Bring a subject to the edge without touching their junk, then portal their dick where a doorknob was for the next person that comes through." Trying to find the right cross-section of light-hearted and delightfully perverted pranks.

General rubbing with hand, which doesn't have to be sexual, sorta like petting a dog on its head.

The squelching sounds of penetration, farting during orgasm, something like that. Vaginal farting.

E.G; hand holding, caressing/massaging, kissing (possibly multiple kissing options, like the type of kiss and location of the kiss, such as the neck), flirting, romantic clothing (tuxedos, dresses, lingerie), makeup (any gender could apply it, lipstick could make marks on the body),

romantic lighting/background/music options, romantic decorations

(wine and glasses, fancy clothes strewn across the floor, heart-shaped chocolate, etc),

fuzzy handcuffs/other bondage, actual game functionality, like a love meter or something, so on and so forth.

A late game feature to add programmable conditions to automate sex toys.
For example, could add conditions like:

If Climax <= 90% then Speed = 100%
If Climax > 90% then Speed = 0%

or stuff like

For 1.0 Seconds Speed = 100%
For 0.5 Seconds Speed = 50%

They could just be pre-made logic blocks/options that don't actually require programming knowledge, just a selection of "Conditions" and "Actions" you can choose from and add.

First person VR support

e.g. knotted horsecock on a wolf

I know this is not a thing for everyone, but hear me out. In the preference option your can adjust a slider for animal genitalia on test subjects, as well as (un-)natural fur colors, so that idea wouldn't be far off. Maybe you could add a slider that basically manipulates the probability of that occuring (setting it to the lowest setting disables it completly) and if a subject is selected by that method it will have a random set of privates.

Of course I would understand if that is too difficult to program. Some additional input would be nice.

Additional options for a chosen special like

Sharks -> Claspers (dual penis)

Female Hyena -> fakepenis

Kangaroo -> balls above penis

Fossa -> double knot

Feline -> Barbs

Or maybe make a list to combine options like

Barbs + knot

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.

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.