going along with @gurun's idea, there should be a clear connection between the basics and the more advanced, and ideas for how to get there.
For example, going through the tutorials taught me different data 'things' could be stored as fields in other 'things'. However, I ran into a situation where I needed to have 3-4 different things together, but always ran into road blocks keeping me from getting it there.
It wasn't until @romanmg helped me out by updating a test app like above, that I realized the design flow of creating different kinds of data, and getting it to work together. Starting with one thing, then the next can be added. How do you choose that thing to begin with? etc. etc.
So utilizing basic skills in a more advanced kind of way.
Also, I would really like to see different high lvl users contribute to this.
For example, Have a couple of lessons from Nigel, some from Gaby, @AliFarahat, @mishav. I am sure there are more, but I know these guys have been super helpful in getting me to where I am today, and believe they have a some unique things to contribute.