Hmmmm, I don't really get how items can be a reward for playing however long the game is gonna be. I played games with a similar idea you put in, one that comes to my mind is persona 5. Putting aside the fact that the game was not made by a small indie team. Some of the core working should be similar. You have a relationship with someone and you try to get them as high as possible, and after beating the game you get a key item for new game plus that skips the grind for later to help play the other core workings better. While That works well in that game, I cant really see it happening here. at least, i don't know if its gonna work to that degree. You have to work with that goal in mind, and seeing as this is gonna take years to do and is subject to change.... i don't know, maybe its just me overthinking it.