Welcome, keep the picture of your project coming........... We like pic's!
My Dh and I purchased a 85 Casita
and were going to rebuild. But finally found what we wanted with a newer model year. But I had spent some time searching for options/ideas for the walls.
one option I really like was a Airstream rehab-er suggested tuck and roll! I really like that idea. Thought it would be fun. He said they would do it just like a 54 chevy...... For me the "insulation" factor isn't that big. Mostly cause I haven't had to spend months camping in the winter months in it. I can hang with anything for a weekend or two..... You certainly want something on the walls and ceiling but you might think outta the carpet box..........
As far as changing the configuration I was told to be careful as the interior walls are there for structure sake so can't remove them. Have to replace.
Good luck with your project!