Imagining the ideal textbook from a language development point of view

For a few years now I have been thinking about what students need, especially ESL students, to develop their language in a way that can support their academic progress. I have come to the conclusion that vocabulary development is key because this enables 'reading to learn'. And also underpins writing.

So I am interested in a thought experiment: Imagine the ideal 21st century textbook for a university student studying a discipline from the point of view of language development, especially from the point of view of vocabulary development.

Now what I mean by 'textbook' is something like this: the mechanisms that provide the input resourses at the student's disposal. So, I am thinking about the language a student is subjected to, or has access to.
First, some principles of vocab development:
1. There must be repetition of target and retrieval

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