If you aren't going to remove the tanks entirely, let them fill at least 3/4 full and then dump. If you don't the solids will pile up in a pyramid under the toilet. Eventually, it can block new deposits.
The other consideration is zoning laws. If it's going to be visible to the authorities or you list it as you official home address, make sure they allow living in a trailer before you put a lot of money & effort into this.
Otherwise, cladding around the bottom. Even in the Carolina's you can get freezing temps and this will help. Also consider heating pads for the tanks and plumbing that is exposed.
If you can shade the unit, that would help with summer cooling a lot.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV