-nodnods- I wrote a supplement on "Trade and Professions" to try and add additional roles for players in that regard, but the genesis of the idea was more far-reaching to split the classes into an "encounter" role (tying into power source as well) and a "profession" role for the aspects of the characters outside of an encounter. This would let, for example, the "Ranger" wilderness archetype be fulfilled by nearly any power source and role type, as the wilderness bits (tracking, nature lore, herbology, etc) would be carried by the "profession" role. As you say, this takes the role+power source grid and all the variety, excitement, and flavour that already grants in 4e and supercharges it with another dimension (potentially further enhanced with backgrounds, themes, and splitting species into ancestry and culture...) Natch, there's a danger of making the matrix too deep, so perhaps Ancestry, Culture , Theme, Profession (which could include background), Class would work.I love the list. And for the most part agree with it.
But I have an observation about the list that I want to couch in the most positive (+) way - every point on the list that focuses primarily on a single pillar of play focuses on combat.
Instead of Utility powers that could apply to combat or could apply elsewhere as a sort-of nod to "everything non-combat", I'd love to see progressions of powers for other pillars of play as well. Roles for other pillars of play. Which means have the same sort of tactical robustness to require mechanics and multiple approaches.
Heck, pick a power source and then pick a combat class, a social class, and a discovery class to match. That would be 4e, but more-so.