Well, I agree with you that a 'grid' was never, and should not be, the goal of 4e. However, you'd still want to cover a fair amount of this conceptual space.
Sure, but what I think this points out is that perhaps this isn't really 'role' per-se. Not in the same sense that the combat roles are. I mean if 'Specialist' really effectively just means "you have a very focused set of skills that you are really good at" is that a role or is it just a character build style that pretty much anyone can accomplish with most characters? I mean, I don't see a specific character element you would utilize to produce that. Perhaps you could construct a VERY general feat that said something like "pick an area of specialization and whenever you're skill checks fall into this area, gain a +5 skill bonus to any check you make" (this would actually just be a mechanical enhancement of the suggested +2 bonus you can get due to a related background element). Not bad, it would convey some element of being focused in a particular area, but at the same time its not very defining. Now, you could probably make more specific variations of this for different specializations, that say added a Practice into the mix or something like that. So, its not a terrible idea by ANY means.
Now, I'm not sure what you could do with the other roles in your list. Some of them do suggest one or another thing, like 'Finisher' might be good at Aid Another, narratively providing that final 'cherry on top' bit that makes something click. I think in that case it might apply to basically any check, Finishing isn't really domain specific.
Shaper might be able to remove failures in an SC, or grant advantages. Plant might be able to substitute a knowledge skill for some other skill, etc.
So, your list could be productive.