What part of GURPS is equivalent to +1/2 level to all skills, saves and attacks?
To be honest, I don't have the books in front of me, so I cannot answer that. But, then again, what part of D&D is equivalent to having a 100 point buy (or whatever) character? The exact mechanics are not really the issue. The point is, every single GURPS character starts exactly the same. You have X points to create your character. No character has any niche protection and all characters can access exactly the same elements and use the same mechanics.
Who says there is one correct response? It depends on what the persons wants from their gaming experience.
Agreed
I strongly disagree that point buy systems in any way show this to be wrong.
However, I will agree that in a very general assessment it is true that mechanical diversity may be set aside without losing diversty.
It is not true that all systems with unified mechanics are overly homogeneous. It just happens to be true for 4E.
In your opinion of course.

Like I said, I don't know. Is 4e "overly" homogenous? I'm not qualified to answer that. And, I highly suspect that you aren't either in anything more than a "for me" sense.
But, feel free to keep stating your feelings as facts.
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Back to the OP. Ok, so you want to add mechanical complexity to 4e in terms of character options. First, I would suggest a couple of goals before you dive in:
1. Don't mess too much with existing mechanics. If you're going to rewrite the system, use another system.
2. Look for areas where you can add options where none, or at least few, currently exist.
Looking at 4e, I would think that a synthesis of the old 2e Kit system bolted on to the chargen system would work nicely. The 2e Kits were, by and large, non-combat oriented which means they won't strongly conflict with existing 4e mechanics. I would work to identify a number of archetypes and concepts that can be expressed through bonuses (or penalties) to skills, social interactions and perhaps some flavor balance in there as well.
For example, a Courtier kit might give you bonuses when dealing with certain people, and penalties when dealing with others. It could open up a couple of skills a class skills and perhaps close off another. I would probably have the kits scale by level, perhaps an encounter or daily level power every seven levels or so that is mostly non-combat. Perhaps at 7th level, the Courtier could use a Daily power that lets him succeed at a knowledge check related to the kingdom or something like that.
I'll admit, I suck at creating new mechanics. But, honestly, this would be the direction I would go.