Though the precise dimensions are different, the final result is a lot like this mockup. Later, I have had an endless supply of coroplast scraps to use for "story sticks". IMO, the key to making peace with Coroplast for mockups is to have a quick and easy way to cut it. After a while of using a nice utility knife in combination with a drywall T square, I built a pair of custom cutters, one for full depth cuts and another for partial cuts to make corners. I can post pics of the cutters if there is interest.
Coroplast is essentially cardboard made of plastic. 4'x8' sheets are inexpensive at my local Home Depot. The white is utilitarian, but I think the clear version looks cool and am considering using it for my final paneling of walls, cabinets, etc..
The cool thing about DYI, is you do what you think best! In my case, I decided to use propane for cooking and heating. I have a temporary BBQ propane tank now, but I plan to mount a horizontal tank under the RV as several others on this forum have done. I camp off-grid a lot in the cold. I did the math, and, IMO, trying to heat with batteries was not realistic. You can heat with gas (or diesel), then cook with electricity, but I kind of like the idea of adding capacity with a second fuel tank. And propane is well understood and costs less.
I really dig lion battery systems, but, after some research, I decided that the lion supply chain for RVs wasn't mature enough yet. For now, I'm doing something cheap and simple - I added 1 AGM house battery and I'm charging it from the van alternator.