Cob Add on to an old Stick built cabin?

Totally uneducated about this so bear with me.

I bought a property that was trashed but a total diamond in the rough. There is an old cabin that was added onto but poorly. I want to demo the additions and create cob add ons at the attachment points that have already been created.
Both additions don't even have foundation, just build on a few free floating bricks stones or earth in some spots and the kitchen addition is just on about 4 inches of freeform quickcrete. The original cabin is on some sort of foundation from the late 1800's and I'd like to add cob... Am I insane?

Photos would help.
As for insanity, thats harder to answer!

I would not demolish, I would rebuild.

Most places that want building permits allow renovation and repair without a permit.
If you demolish you may need a demo permit and then have to apply with drawings etc for the replacement.
I would pull one wall away at a time, rebuild properly and move ahead.
Cob, mudbrick etc are all good.
What is the original one built from?