If it's Renpy: the ability to use the mouse wheel to go back, and the "right click to save" option enabled. They are major quality of life improvements for me. In the event it is an RPG Maker game (or any sort of RPG, really) a readily accessible "compass" system to tell you where you should be going next, and the ability to both manually set gear, as well as auto equip the best gear (especially if there is a lot of it, or random drops). Finally, for any game that shows up on here (i.e. based in lewdidity), a gallery of some sort, or an option to repeat events, is always a nice touch. I'm sorry I can't give more specific suggestions, as I'm not sure what your project is about.