I'd suggest to get your best price and make a commitment to either get under the trailer yourself or hire someone to straighten out wiring and ducts, insulate, reinforce tank straps, and install a covering on the belly.
An owner can get a much better result underneath than a factory, in most cases. After the sale, you can design/upgrade the under-belly to your desires and your need for access.
Just a few upgrades off the top: Reinforce tank attachments to carry weight of full tanks, insulate with foam board and batt insulation for comfort, dress/route wires for OEM operation and any future electric use, insulate heat ducts, route brake wiring in a "star" config.
I've actually done this using 2" foam board and Luan sheet goods. The Luan board was sealed thoroughly with paint before installation. The increase in comfort was big, no more cool floors. Foam board was glued/sprayed into place and the Luan was installed with flanged screws, into blocking, if needed.