Well, in order for you to mod something you'd need a different loader (Thus, like games similar to Terraria or Minecraft), as well as a coding API WITHIN the loader, as well as a platform that allows users to make the mods in question.
You'd also need to use a powerful programming language, like C++, Eclipse, Javascript or whatever language the Developer uses in this case.
And it might be hard since the Console is a relatively recent addition, and he hasn't disclosed what language he's using.