I'm not much of a gamer nowadays, if at all; I used to be one in the '00s. Most of my inspiration comes from that time.

I think the main requirement I have is that it would be a legit game, just with lots of "perversion potential" to it. Something that you can actually play seriously if you want to. Saints Row probably comes close - you can either play it as a goofier GTA, or you can run around in sexy clothes and kick strippers in the groin.

The core concept of my "ideal game", described below, is heavily inspired by Severance: Blade Of Darkness from 2001, a 3rd person slasher / fighting game with swords and other such weapons. I doubt that many people here heard of it, but it's considered to be one of the early cornerstones of the genre and has aged very well. It has a fantastic combat system where every slash and blow feels heavy and the momentum is clearly seen in animations, and you can't just click spam your enemies or jump around the room. Block, parry, dodge to the side, block again, slice across. You need to actually master the mechanics to survive. It's quite hard, but not outrageously so. Lots of blood and dismemberment too, but it feels very appropriate in-game.

Back to the topic: the game I'm thinking of would similarly feature a detailed combat system where you can't just mindlessly click everyone to death. Weapons naturally include swords, spears, axes of all sorts. Like I wrote above, it probably would have a coherent storyline, characters of all genders and adequate armor, but you can also optionally turn it into a fetish fuel full of half-naked girls. Like Severance, it wouldn't be about huge battles, it would be about tense skirmishes, like 1 on 3 at most. 1st person or 3rd person, you could probably switch between the two, although 3rd would be my personal preference. Doesn't have to be open-world, I'd take detailed medium-sized locations over huge fields any day. Think of something like a fortress that you're sneaking into, that sort of stuff. And perhaps a Coliseum-like arena or some small enclosed rooms for the arcade mode.

It's an unpopular opinion, but the graphics don't matter that much, imo. Instead, the animations, the randomness, the sounds is where it's at. Sure, I wouldn't mind incredibly high poly models and all that, but honestly your mind fills in the blanks anyway. What about making each encounter unique instead? Not just tons of possible animations, but introducing a fair amount of randomness to them. Even your character won't be surgically precise and might mess up an attack here and there. And, of course, each reaction would be essentially unpredictable. If that girl's stomach is sliced open, does she fall to her knees, shivering? Does she keep fighting? Does she stumble back away from you? Of course, it would be composed of pre-programmed animations, but the randomness should take care of obvious repetitions. Reactions are a very important part of the experience, probably even more so than the actual possibility to inflict a particular injury.

The latter is also an example of how most popular game mechanics collide with real life. Think of shooter games - do you honestly think a person can take several bullets and keep running around as long as their health is above 0? And the more "realistic" the game is in its depictions, the more jarring this dissonance will be. So most likely the damage received directly impacts how the character fights, and the wounds need to be treated asap - think of stuff like tearing the arrows out, cauterizing the wounds, etc. Perhaps this could be implemented as a separate screen where you can examine your character's body in full HD detail, read the suitably clinical descriptions of injuries, and apply fixes (which would be shown, of course). Some things can be fixed fairly "easily", while others are more like "bandage that shit up and hope that you can get to a doctor within 2 hours, the clock is ticking".

Oh, and armor actually directly affects the sustained injuries and their nature, instead of making specific body areas immune to damage or being just abstract hitpoints.

I briefly mentioned sounds above, and they are also important. Grunts, moans, screams, wet sounds of metal slicing through flesh, all this stuff complements the visuals. Characters making a reference to what has actually happened to them ("Argh!.. not... in... the... gut... FUCK!.."), all these subtle things. Lots of different voices, very little repetition, if any. I think it's an aspect that's often overlooked, proper sounds can be as sexy as the visuals.

Replays: the last minute of gameplay can be replayed from any angle. Perhaps a "cinematic mode" where you can make high quality cinematic renders, as opposed to just "regular" graphics settings (like I mentioned above, it's not that important during gameplay itself). You don't notice much when you're playing anyway, but these replay frames can be rendered in full detail, complete with subtle motion blur, color grading, droplets of sweat on the skin, blood flowing out of wounds and everything else.

Detailed character creation screen, and maybe an option to use reference images (although we all know how "well" it usually works...). Perhaps some general sliders for other characters; i.e. do you like athletic girls or skinny girls as your opponents? The game will try to keep this in mind. For example, I personally would prefer a fit amazon who wears little to no armor just because she feels badass and confident, instead of a bimbo in what looks like bad cosplay, but to each their own. And this is also where that aforementioned "serious game vs. fetish fuel" slider is located.

And speaking of enemies, while most of them would be human, you'd have to find unique approaches to them. Maybe the forest amazons are very offensive while the "knights" are very defensive; or those Asian girls have shields that leave their left side more vulnerable, this kind of stuff.

Lastly, and it's a very specific personal preference, but all sorts of groin attacks of varying gruesomeness.