Since I have already been asked why we didn't just tear the house down and start over, I think we have to draw the line at putting all new studs in. My first preference for walls would be SIP's. Second would be 2x6's. The fact that we are stuck with the 2x4's prompted my original question. If we can't have the ideal, can we make the best of what we have?
I'm not sure what fire stops are required, but I will check with the architect to make sure we comply.
Thanks again for all the input. I think I speak for a lot of people when I say we appreciate all the time that people like you and Jim Rogers devote to helping with our various challenges.