If you'll allow me to play thread necromancer, I'd like to second two of ben's suggestions and add two of my own.
Firstly, adding dialogue to the scene replay in the mansion. I suspect this is already planned for a future update, because you can select both versions of Mary's Holiday Outfit scene, which I'm pretty sure are identical apart from the dialogue. It would be even better if you could choose which scene variation you want to see. Some scenes change multiple times over the course of the game, and it could be fun to revisit an earlier version.
Secondly, adding shadow walking to the player character's permanent arsenal. Given that you're always trying to avoid enemies rather than fight them, it feels like a more natural extension of the gameplay than the slingshot. But they're on separate keys anyway, so there's no reason you can't have both, with some enemies being immune to one or the other.
One thing I have to disagree on, though, is the issue of tension. I actually like the lack of any real time pressure in both the overall story and the interactions with each of the girls. I play games, especially pornographic ones, to get away from the stress of real life, so why introduce artificial stress?
As for my own suggestions, the first is adding a new section to the theater for sprite animations. I don't know how hard this would be to implement, because many of them (like Raylene getting spanked in her bedroom) rely on a specific context. You might have to move the player to a static replica of the area each sprite scene could originally be found in.
The second is allowing the player to return to a character's mind dungeons after completing that character's story. This could be done by giving each girl a diary, which you can use to 'reminisce' about the events being described. As it stands, the chests in these dungeons are more or less the only missable content in the game, and some players may just want to repeat the minigames for their own sake.
All things considered, this is already a great game and I have no doubt that future updates will make it even better. I'm eagerly speculating about the significance of Mary's wedding dress, what might happen in those two unused rooms in the inn, and whether or not Fae could help me learn some of Auri's language. No matter what direction the game takes from here, thank you and good luck.