(Relatively) briefly, on your steps, I wanted to say that Art of Problem Solving (the website where E is taking math classes) does basically this, because AoPS is awesome and they have thought a lot about pedagogy for bright kids. (More on this later, hopefully.) From our experience with them, I would add another Step 1.5 to your steps, which in my opinion is super important: If possible, have there be an easy, accessible way to ask for help during the process of problem-solving (before they submit answers), and normalize it so that kids are encouraged to use it and know that it's something everyone can and should do, not just kids who are "behind." In particular, AoPS has "office hours" (all done openly-to-class and in text) as well as a public message board where kids can post questions openly, and both instructors and other students can post hints and clarifications (though not, at this stage, actual solutions). They strongly encourage everyone to use these open-to-entire-class methods (to the extent that it's rather more difficult to contact the instructors privately), and I also strongly encourage E to use it (instead of asking us, when possible -- although she can use us as "rubber ducks," which is often what she needs).
Of course it's not exactly the same, but you can see the application to starting to encourage modes of thought analogous to collaborative problem-solving in grownup jobs! Pedagogically, as well, most brains (idk about yours, as we've talked a lot before about your brain working in nonstandard ways in ways that may intersect with this) work in such a way that learning through doing the problem when possible, even with hints or some mentored help, is way, way more efficient than not knowing how to do the problem and then reading the solution and then getting another problem. (In addition, it also encourages the "working through not knowing how to do things" skills. And logistically, there may a limited number of good challenging problems at the appropriate level available for the particular topic.)
Re: Another book rec
Of course it's not exactly the same, but you can see the application to starting to encourage modes of thought analogous to collaborative problem-solving in grownup jobs! Pedagogically, as well, most brains (idk about yours, as we've talked a lot before about your brain working in nonstandard ways in ways that may intersect with this) work in such a way that learning through doing the problem when possible, even with hints or some mentored help, is way, way more efficient than not knowing how to do the problem and then reading the solution and then getting another problem. (In addition, it also encourages the "working through not knowing how to do things" skills. And logistically, there may a limited number of good challenging problems at the appropriate level available for the particular topic.)