A few TC questions about host trucks and factory add-ons

I was thinking if I went with something like the Douglass/SherpTek bodies, I could house additional batteries in there? I definitely want an electrical system similar to yours.

I was also thinking maybe a water pump and filter so I could replenish the water supply....though now that I think about it, that'd mean dumping the black/grey water somewhere, which means I could resupply water as well. LOL