I really like the sound of that wall, and I like the look of the timbers with the plaster coming up to it as the inside finish.

I'd like to come up with a way to keep the air infiltration down, personally. I live in a drafty old farmhouse now, and when I build a new one, I'd like it to be a little tighter (and so would my wife). I suppose the biggest problem areas would be at the timber/plaster interface.

I'm also thinking about having 18" or so tall dwarf walls and a timber sill on top of that. And hopefully an earth floor with radiant heat in it.

You could hold the plaster back 3/4" or so from the face of the timbers to add some visual interest. You could have the baseboard die into the corner posts... You could hold the braces to the inside face if you wanted to see them... nice curvy braces...hmmmmm.

I have to think about this some more. How hard is it to learn how to plaster?