I could be wrong but my guess is that the storymode the devs are planning to make will be like MonolithBay in terms of having a set of interactable characters (that can be customized) and being an Adventure with a bit of a linear story.
A thought that has been circling me around is how nobody has suggested about making H.T like Koikatsu in terms of:
#1 You build the population of NPCs (or pick the standard ones) that will be roaming around (in this case) the neighborhood.
#2 You can interact with them but MOST IMPORTANTLY, shag them.
For more variability, NPCs will have personalities, traits and relationships with other npcs (like the Sims) that will make them easier or harder to progress your goal of persuasion (i.e: a lonely housewive must be approached with discression, lest you get catched by her (lazy) husband), however, to make it more than a sex game, you have to earn money, level up stats, earn traits, tidy up and upgrade whatever place your living in.
So you get the idea about making the core aspect of the game more sandbox'y and replayable, it could also have the option to choose a female protagonist (no penis mode) and "woo" the men, the women, the futas, the femboys? Whoever you want.
The TL;DR = SUGGESTION: the Sandbox should be the "Campaign"-mode, where you can seduce (or voyeur) EVERY NPC, you have many ways to approach them, making for unique scenarios and increased replayability.
PD: If you're wondering how i came up with this, i just took a shower after "post-nutting". (Also as i said in the first 4 words, unless the Sandbox is just like the above thing and not a sex gallery, this whole comment is product of a nut clarity and you should call me dumbass
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