Inspired by your mod I decided to make my own. So basically you can mod stars to always get 3 of them.
There is a method in StageManager called CheckStar(...).
There are a few ifs u can just comment out and leave starInfo.star[x] = <number>; only, and it always gives you 3 stars at the end...
Then you don't have the latest version of the mod. You just go to Ella menu, select your girl and click Upgrade, the Upgrade button should be always activated, but don't go over max cuz the game freezes.