Rails' convention-over-configuration approach can confuse newcomers when debugging request flows.
Create a tool that generates interactive sequence diagrams from Rails apps, showing the complete request lifecycle from router to controller to view.
Offer a free web version for simple apps and a paid CLI tool that integrates with larger codebases.
Start with basic routing visualization, then add middleware, concerns, and background jobs.
The risk is limited audience - experienced Rails devs won't need this, so growth depends on constant inflow of new learners.