I'll reply here instead of
here, because Frank's cat always makes me smile.
I've entertained the same thought about my Clark Cortez motor home. It weighs 9000lb. If I replace the steel body with wood/bamboo and a lightweight interior maybe I could get it to 6000lb.
For your purposes, though; maybe a 'Class-C' approach–where you retain the original cowl dash and windshield and replace everything from the door hinges back?
I did this for another thread you can find
here:
I'm hampered by my facilities; all my tools are jammed into a little shed. How are you fixed for shop space?