I can remember a long time ago; back on the old website where I tried to convince Josh to take an approach that was a cross between blender game engine and CryEngine2. Looks like we are finally getting there with thingoids + Kismet/Flowgraph. While you guys are designing this stuff you might want to take a look at Blender Game Engine. It's quite smart the way they've done things. I'm thinking you could build some concepts from their implementation.
And before you scoff at the notion (not to be presumptuous our anything); keep in mind blender has SSAO, HDR, Bullet physics including softbodies, shadows, all kinds of post filters, scripting, trigger volumes, raycasting, etc etc etc, in fact the only thing they don't have is deferred rendering. In other words, it's quite a mature engine and I think you might want to study it for a bit.
I've said it before but the Blender opensource project in general is to 3dsMax as Leadwerks is to CryEngine2. It is really elite calibur software. And if you find it difficult to understand it's interface right away, I can help you to interpret it easier as I've been using it for years.
You guys are doing phenomenal work already and I only mention the idea of closely looking at blender because I think that it could be beneficial from a design standpoint. A lot of things you seem to want to do have already been addressed in Blender. Not that they couldn't be improved in some fundamental way but again looking at them might not hurt. If you haven't already that is.