Todd...are you working with a timberframe supplier? They deal with this stuff daily i'd think and would be able to give you some good feedback. For my TF i just did normal stick construction outside of the TF and held the stud walls off the TF by 3/4" so that i could slide drywall against the studs but behind the TF posts/beams. Doesn't sound like the look though that you're after. The advantage of the approach i took is, to a normal framer most everything was what they were used to.
The other approach which is a little closer to what you're doing is the SIP panel route...but i'm sure you know how pricey they are.