@Gargron Funny story, I have been incubating an idea for some months and it's really similar to this, I wasn't aware of Solid existing. So I'll have to choose whether to continue or focus my efforts on helping Solid. I was planning on using OAuth + GraphQL basically.
In case you want to check it out these are the repos where I started tinkering:
https://noeldemartin.github.io/autonomous-data/