This has been of course accompanied by me trying to look at and think about various chunks of D&D rules over the years. In my latest post in this vein (here), where I wanted to point out a line between Ability scores and Class-based "powers".
I've just read Mike Mearls' latest column, here (and here is the RPGnet thread that alerted me to it). I wanted to quote selected parts of it but it's better that you just read it all, especially everything after the "The Mechanical Core of D&D: Abilities" heading. You can also go back and read Mearls' last few columns (going back at least to "The many faces of D&D", but it won't hurt to read back to "Combat and other forms of violence", his columns are pretty short anyway.
So, with much of what I've been writing and thinking about D&D lately, I think I've caught more or less the same wave as Mearls or at least the same break in the reef. (Pardon the surfing metaphors, I've been reading Inherent Vice) Getting right down to it, I think all you need for your character is a name, description, the six scores and a d20. That's where we start. Then we add, as minimal and open as possible, the core D&D-isms: AC, Alignment, Race, Class, HD/HP & Damage. At this point they don't really do anything, we just know they're there. Everything else is modular and optional, so you can easily scale the complexity of your game up and down without really losing anything. That's the idea anyway.
EDIT: If Mike's columns imply that WotC is actually working on this mythical "core D&D" behind the scenes (and that's a big if), I think I'll happily throw my own work away and endorse it.