The RNS will require either a lot of content or some kind of random sentence generator based on a word list, maybe both. Upon some basic research, there are some generators developed in Java, which could be converted into Unity or Unreal. The veracity of these generators may not be technically sound at this point, and may only require a load of content.
Monitoring the students progress is always key, and I feel there is an absolute and direct path towards tracking progress and understanding of the content. Through the ?understanding? of the content, through grading, or even peer review, this system will offer the educator insights and metrics based on the students' progress. Utilizing this data the educator will be able to adjust the flexible system to better suit the current needs.
This will require an understanding of how content is judged by difficulty between the educator and the student.