I'm still trying to decide the possible endings, though. Aida is a tragedy but many creators say most people don't like bad endings in this kind of games, so I guess I have to create a couple of alternative good endings (or just let the players imagine what happened next according to their tastes, like in 'ok, everything indicates this is going to be the end for the characters involved in this scene but the game stops here so you can think they still managed to find a way to avoid their fatal destiny'). Comments and suggestions on this issue are welcome -and encouraged.

I've decided to use the male character (Radames) as the PC, so both women (Aida and Amneris) would be NPCs. Players will know later in the game how both NPCs reacted to each PC's decision, which should explain why the player got that ending (obviously there'll also be small adjustments along the game according to previous choices). This script is already written (in Spanish) and tested in Ren'Py, and as I've said before I just need to add the alternative endings. But I've also thought I could do a 'double' game, allowing the player to play alternatively as Radames or as Aida. So, instead of reading a linear story (with some sex attached) just before the end, you'll get the missing info by playing as the other character. This will make the game bigger and more complex to finish in terms of development because I'd need to come up with some significative choices for Aida's role as well as some extra scenes and endings from her point of view. But I'm on it.
Now let's talk about the art. Well, I just can't make pictures. So I'll need to work with an artist. 3D, 2D, cartoon, hentai... I don't have any preferences, I just want the pictures to look good. But for now I just want to focus on the script and then, once finished and knowing the aprox amount of pictures needed, I'll post a partnership offer on this thread. Sex scenes will be negotiable (I can script them all, I can give some basic ground or I can give the artist complete freedom to do what he/she thinks it fits the characters and situations and then just write a matching text). I'm not a big fan of crowdfunding so I'm not going to launch a campaign for this game. Period. But if the chosen artist happens to have a p*****n page or something like that, well, we'll discuss it later. Also, I'll probably need an English-speaking native to check my traduction when it's done. But it will take some time to reach that point of development.
I'll keep updating this thread, thanks for your attention.