I may be lazy, but I don't have enough dedication to commit to reading a full fledged story and learn about characters and such. I mean, if it has good writing, it might be interesting. In my opinion, a good porn game has a mix of both porn content and a story, but it absolutely doesn't have to be Tolkien tier story, in a matter of fact, I'd rather prefer something simple. But who knows, I don't have tons of experience with VNs, the ones that I've played and enjoyed both porn and writing are Amorous, Juicy Futa, Femboy Burgers, Sissy Maker Deluxe, and that's about it.
This why I don't think I will go with full VN style but rather Manga/Anime, shorter sentences, faster pace, story written though the discussion of the chars rather than a pages full of writing (might do that as side info, for those interested in lore, species etc).
This method is also asking way more cg/work as even the lips of a chars should change to see the emotion that goes with those lines, but to me it's seems essential.
For the story itself, it dosn't have to be Tolkien tier true ^^, but there are good and badly written simple ones (same for complex ones).
I decided to go with the adventure type of story, I can imagine a complex world and slowly unfold the story around it as the player dive into the game, while the background story is interesting, the adventure type still resolve around meeting different chars, not everyone is about to backstab you for power in an intense political intrigue ^^ (I can do that to! But that won't fit this game xD)
For character writing is not much about taking time to learn about them more in this case, what's make this character slightly better than the others, maybe my point will fall flat on this one xD
Ex : In those game you quoted is there a char or two that you would like to see more content of it? That could be because of it's chara design/writing
Some point may be off, you can tell me if you disagree^^