"I've been meaning to respond but I've been very busy."
Same here, I figure it's just that time of the year (I was getting a bit worried that there had only been like three posts across the entire site for about a week, though :))

"My first observation is, why worry about making the inner framework in your walls structural? This seems to me to be creating a lot of unnecessary joinery without a whole lot of benefit to the structure. My approach would be simply to make an inner curtain wall and let the outer wall do everything structurally."
When I went to look at designs for floor/wall/second floor joint layouts (each post spans only a single story to keep costs down), it struck me that the column assembly is significantly weakened by the presence of the cuts for the floor joists, as well as their off-axis loading. By splitting the column into two layers, the inner layer can be carved up to support the floor joists, leaving a simpler and more uniform outer spliced column element. Since the structure is only two floors, the second layer of (more weakly jointed) interior posts would support the less structural internal roof rafters, while the outer column would bear the brunt of the roof loading and deliver it straight down (stabilized by cross ties with the interior layer).

Basically, it seemed like a convenient way to split up the loads applied to vertical support posts in order to simplify the engineering side of things, if not assembly/construction. Since I plan on having a generous walkway cantilevered on the exterior opposite the interior floor joists (i.e. joists on both sides of the wall in some form) it may not be worth the trouble. I do still like the idea of no more than two or three timbers intersecting at any point, though.

If I can find a diagram of a wall joint layout where;
-Two columns are stacked/tied together along Z
-Two floor plates tie in along Y
-Two floor joists tie in along X
pretty much like an interior frame junction, only the result doesn't remove so much material from the members that another row of supports (i.e. an exterior wall frame) are not required to stabilize. Rather demanding task, I know.

"You are right that such a system could be more efficient from a materials standpoint. However, I would guess it's a lot more work to do and far less efficient from a labor standpoint."
I agree completely, and if it is not needed (see above comment about the spans involved) I'd just as soon not go this route. However, the complexity, I hope, is less of an issue than it might be, since my floor plan is basically a lofted arrangement, with only half the upper floor, floored (the remaining half of the octagon is an open cavity). So if it's twice the trouble, it's still only half the square footage. Or something.

TCB