not a suggestion but why didnt you try to make all gamemodes multiplayer?
Viewing post in Baldi's Basics The Ultra Decompile comments
Multiplayer took about 2 years to complete Although you would think that it would be easy to implement it for all modes, it's really not. I can't be bothered to code more since I have to be careful for performance, bugs, and functionality. I decided to keep it simple and leave the classic schoolhouse to be the only mode that has multiplayer.