This Venn diagram approach is highly intelligent! I love the metaphor from the product design world. I also agree that motivation and consistency alone will suffice to access the knowledge (at least in my case).

This is pretty much how my entire Finnish journey went.

I think there's one small missing nuance worthy of further exploration (maybe in a new article). How does one go about getting this "specific knowledge." Do they brute force the language like I did with my Finnish journey?

With Finnish, brute forcing (trial and error) was a basic requirement, because the learning pathway is so poorly documented for a semi-independent learner learning 100% outside of Finland. Immigrants who take intensive formalized classes in person in Finland get to the B1 level in 2 years.

Some other alternatives to get this knowledge might be seeing how another learner did it or modeling a process that worked previously with another language. I did some of this too, but there might be other ideas.

Excellent article! Great work!