I suggest you add a 4th floor to the schoolhouse. (The top and viewing point of the schoolhouse)
Add a mode named "Plus Mode" and add 5 floors to the mode. It has to look 100% like Baldi's Basics Plus.
Floor 1: 4 notebooks
Floor 2: 7 notebooks
Floor 3: 8 notebooks
Floor 4: 7 notebooks
Floor 5: 10 notebooks
Add new achivements: The Innocent (Beat Plus Mode by failing all notebooks)
Unbelievable (Failing all notebooks without cheating in Plus Mode)
Add the light test room (lots of button and switches and the shrink machine)
I suggest you add a shop in the modes (You go in an auto door, and Johnny talks like in Baldi's Basics Plus. Add a display of how much money you get to preview with the price of the item you will buy.
Add those in the mod, and change the mod version to V3.1.