I usually stick to the ingame music, but when I listen to something else... it's usually the soundtrack for another, because statistically, that's what I have the most in my music library.
Yeah, I would be wary of how complex the project would be, sandboxes can get complicated fast. There's also a risk of the game being "bottom-heavy" so to speak, where there's a ton of content in the early parts, but things dry out quickly as you progress.
Scat & watersports, I also kind of cringe whenever I see oversized body parts. Feet don't really do anything for me, so if over-focused on, it can certainly be a turn-off.
Porn has an age-old bias towards producing stuff for the average heterosexual male. Given the market size, there's gotta be some VNs out there that your partner would find appealing, but that's gonna require some searching.
ps.Let us know how it goes.
This aligns somewhat with my own thoughts, I think it's kind of difficult to translate an anime art style into 3d, especially for an indie dev. It can absolutely be pulled off, game studios in Japan, Korea & China have become fairly good at emulating that kind of eastern art style into 3d games...
I think overall, I've liked more games that are tagged as using daz, but I have been around enough 3d modeling communities to know that the artist's talent & experience with a given tech are the primary factors for good artwork.
I've been on the internet long enough to know that lolicons & shotacons are far more common than people think. It doesn't make you weird by itself, and if it doesn't affect your life outside of your porn habits, it doesn't make you dysfunctional.