This is super interesting! I'm glad to see new ideas about how speculation can be so powerful. I was exploring this in 2016 with "speculative education" and wrote a little about the potential high level concepts here: https://charliegedeon.medium.com/using-details-from-conversations-to-enable-further-education-5d9d2ab82000

Have you ever tried tools like Kialo? I know it's not exactly speculation, but the tree-diagram interface could lend itself well to speculation as well!