I disagree that the 4E framework cannot support this. I value your concerns, although I would appriciate knowing if there anything in detail that you object to.
On the balance issue, I would think it's clear. Frex, a 10th level combat encounter assumes players have powers/feats/etc at 10th level. If they've spent these on features not useful in that context, then they're not as powerful as a characters of their levels are expected to be, and then it's not a balanced encounter.
I suggest that 4E is a combat orientated game as written purely because it lacks creative and academic type skills, non-combat roles, and a progression for an ordinary person to become a hero, for example.
I'll agree wholeheartedly with that, though I submit this is by design, not omission.
I like a lot of the mechanics behind 4E, but I think, and my players agree, that it feels a bit like 'Fisher Price My First Roleplaying Game'. Combat in the games I run accounts for less than 10% of the time where as creative, investigative and social skill use accounts for 50% or more as this is woven inseparably into the roleplaying. If my players like this type of roleplaying, why should I have to tell them otherwise?
You shouldn't of course, but then if combat in the games you play is less than 10% of the experience, why play "a combat orientated game [system]"? Seriously, have you considered this? There are a plethora of good systems out there which are more role-playing oriented.
(Judging from the 2000+ downloads I suspect that at least some of the readers of this thread agree with me)
Volume is a spurious argument. Just because the entire town drags a witch to the stake, that doesn't make her a witch.

BTW, I'm one of those 2000+.
If 4E is going to support playing styles beyond the 'Monster of the Week' syndrome I believe that it needs an optional depth.
Again, I agree. I just don't think it ever will, or can, without making changes so significant that it's no longer the same game. The resultant system may well be spectacular, but it wouldn't be 4E, leading back to my "different system" argument.
Again, I value your feedback. You mention basing the new skills on existing 'primary' skills. I did consider a similar mechanism, but could find no existing skills that where even vaguely suitable - do you have any suggestions?
And I'm trying to be constructive (believe it or not

). I think the only way to maintain game balance is for PCs to still have the same pallette of skills/feats/etc with something like this tagged on. I can understand the dilemma in finding suitable primary skills (and now I'm realizing I didn't quite think that one through, this is a tough project). The only thing I can think of off the top of my head would be to give synergy bonuses a la 3.x for trained skills such as Dungeoneering, Arcana, etc that seem applicable to the secondary skill in question.