Where did you find the roadmap you are referring to? All I found for mod support was one line saying they were coming out with a mod manager in the faq section on discord.
It's an rpg maker game so you can't exactly mod it like you would for say Xcom or skyrim, you have make a new version of the game to add the functionality that you want. Unless you want to keep backups of the base game files and replace the necessary files with the ones that were modified.
