One thing I would suggest creating as a marketing tool is interactive guides on books that don't have alot of excersices or are more 'text-booky'. Like a no fear shakespear for some technical book.
One of the things that made me think of this is my current rabbithole that is learning the rust programming language. There are generally two answers when you ask someone how to learn rust, "Learn C++ and read The Book, or read The Book". "The Book" is dense... but i found this program called "Rustlings" that makes the experience much more enjoyable.
Rustlings is essentially a list of exercises, tests and quizzes attached onto the rust book and some of the documentation.
With Slip, you could be the genius.com of open source technical books on top of courses. More detailed explanations, quizzes, courses, etc.
Also, Another field that needs to be disrupted is paid webinars. There's alot of people who give talks on topics and get paid per attendee. If you could centralize that, i'm sure it'd be a good business to get into. I have a friend who gives webinars on certain topics and he uses onlyfans lol.