I wanted this at university and tried to write something similar before inevitable employment and distraction. I wish you every success, a couple of ideas that may be applicable:

Probably quite cheap to pay people to onboard sets of well established notes, eg cambridge undergrad maths notes or similar. This may help with dedicated users in niche communities.

Collaboration is hard, but a forking mechanism might be easy+valuable.

Tree structure could guide spatial repetition probabilities, see eg that half-life regression paper from Duolingo.