What is ReadMe.io missing that you'd like to see?
I'd personally like to see a simpler version that offers a free plan too which students can use. Just like how many B2B and developer targeted SaaS apps offer a free plan that has some limitations but help people to get started.
Students globally are not documenting their code, projects and startups because there is no simple and more importantly free/cheap alternative that they are aware of.
Readme.io is pricey and is simply beyond the reach of students and developers of developing/underdeveloped countries.
Their is no Readme.io like SaaS app for small and budget-sensitive projects as far as I know.