As much as I like your starting enthusiasm, it might be just that.
Other than that, I like the idea. Might you link us pictures of the models you're planning to use?
Considering that Corta's platformer it looks quite horrible
I highly doubt if you can create anything decent alone since all work mostly just models environment and animations while the game itself is not really important part.
If you still want to do something like that I would suggest something very straightforward and short what you could finish in 2-10 minutes without repeating same scenes and same animations.
For guro and sex game something like TROLLFACE QUEST or stickman series or Stupidella games would be very interesting and fun to play and not that hard to do.
Considering animations the easiest way to create graphics is 3d rendering you can use DAZ or MMD. You can also flatten them to turn into 2d
Painting everything by hand is quite a hard job even for a good artist.
I checked out the game you mentioned. It's quite good graphics wise, but the shooting controls drove me mad.
>General Ideas for the game
That arena combat scenario you mentioned sounds hot as fuck to me. As long as it is possible to fight then rape then brutally execute my enemies.
Oh, a bonus level where you just slaughter female slaves for the amusement of the public and yourself would be god tier.
>Requests for animations
a beheading animation or a head bash with a mace, while the girl is giving you a handjob or after you come on her (one of my major kinks atm)
The game you mentioned you could use assets from does a decent job with the kinky attires, but it could be better imo.
Also, maybe a finish her/them kind of sequence after you defeat your enemies - with them naked and begging on their knees. Some might even try to masturbate or lure you with their bodies (i'm probably drifting already into fantasy land) and you could either execute them or fuck and execute them.
Why not use a game engine like UE4 or something? A lot of them are free for non-commercial use.