Since there have been many suggestions about harem and sharing stuff, here are some for Anna specifically that I could think of (Especially for Pure Love route):
1. A Scene when we decided not to go to the church on Friday. Since Anna is such a caring woman, I think it makes sense for her to stay home with MC since the latter said that he's not going because he's not feeling well. That should then lead to a scene of her taking care of us early on (maybe an opportunity for a pic even), which eventually develop to a H scene in the endgame, ala the showering event we already have in the game.
2. Starcon expansion for the pure love route. I mean, they're staying in (presumably, since I don't remember) another city over the weekend all by themselves. There should've been a sex scene here ala the slut route but just between the two of them, nuff said. Even if they're gated behind the costly wedding dress cosplay, I think it's a huge miss here not having any reward for us pure love lovers, lol.
3. An option to drive her home / go on a date after going to the mall on Friday. I think expanding ways to interact with Anna alone when not at home beside the mall event is another thing the game currently lacks. And unlike the first two suggestions, I believe this one can be implemented for both routes, too, assuming you have the time for it, since it'll be a rather big update if so.
4. I dunno if others have touched it, but a way to track your pure / slut points would be nice. If you don't like the idea of sliders since it's a bit too meta, introducing a diary that Anna writes would be a good way to implement it (So, if it's pure it's something along the line of "I know I shouldn't, but I really want to be with him," but if it's slutty then it's something like "Oh my god, I really can't live without his cock anymore!" etc, etc).
That's all I could think of so far. Thanks again for the great game guys, and I hope you all keep up the good work!