I'm not a native English speaker and my writing is worse than mechanical translation, so I'm sorry if the text is a little strange.
For me, the game's base story is good, but you must know that the story must be developed.
About fetishes my suggestion could be developed by steps that seem more natural to me, lesbian GF you can put them watching a movie in the bedroom there is a kiss between two women kissing, the girlfriend comments that she wouldn't see herself doing that, the MC can respond that thinks it's hot (GFles =+), Mc agrees (GFLes +=0). with 5 she starts flirting, 10 she kisses and so on until the point where the MC catches the GF and Andrea in the bathroom. but the bathroom scene will only happen if the player continues to encourage it.
One of the sandbox problems is that there comes a point where it's strange that the NPCs don't notice anything that's going on around them. It's a good thing because of the world's story adjustment could be when all the girls have Stage: 5/5, too. It's a good time to divide your game into capitols to avoid it becoming oversized, and it has the advantage of making it easier to find bugs and fix errors since you can start with a clean version.
You could highlight the lines with color to make identification easier, the MC's color should always be the same.
This is just a suggestion, don't feel obligated to follow the advice since I don't know your project and I don't know your future plans for the game. And don't force yourself to do fetishes or content that you don't like, you'll get tired of the project and the content won't usually be of good quality.
For me, the game's base story is good, but you must know that the story must be developed.
About fetishes my suggestion could be developed by steps that seem more natural to me, lesbian GF you can put them watching a movie in the bedroom there is a kiss between two women kissing, the girlfriend comments that she wouldn't see herself doing that, the MC can respond that thinks it's hot (GFles =+), Mc agrees (GFLes +=0). with 5 she starts flirting, 10 she kisses and so on until the point where the MC catches the GF and Andrea in the bathroom. but the bathroom scene will only happen if the player continues to encourage it.
One of the sandbox problems is that there comes a point where it's strange that the NPCs don't notice anything that's going on around them. It's a good thing because of the world's story adjustment could be when all the girls have Stage: 5/5, too. It's a good time to divide your game into capitols to avoid it becoming oversized, and it has the advantage of making it easier to find bugs and fix errors since you can start with a clean version.
You could highlight the lines with color to make identification easier, the MC's color should always be the same.
This is just a suggestion, don't feel obligated to follow the advice since I don't know your project and I don't know your future plans for the game. And don't force yourself to do fetishes or content that you don't like, you'll get tired of the project and the content won't usually be of good quality.