Christina,
It is possible to mix knits and wovens. 2 tops that I made recently using Ottobre Design patterns were specifically designed for that.
I tried it on the Hopscotch top. It worked for me but I only replaced the front panel with a woven. There’s still enough stretch to get on and off with no problems since all the other pieces are still a knit. I had forgotten until I started cutting the fabric that the armscythe is continued from the yoke to the front panel and worried that the opening would end up too tight in the armpit because of that. I held my breath when Miss M put the shirt on for me to take pictures but it went on easily and she didn’t complain (at least not about the shirt, about having to pose for pictures, YES!). She also wore it for the rest of the afternoon with no complaints.
I did add 4 inches to the width of the panel since I wanted more gathers across the front. The side seams went together nice and flat as you can see here: http://www.flickr.com/photos/27858004@N05/5538228616/ Hope that helps!
Cindy