One repair I've done is to run weather stripping around the escape and mangers doors to try and prevent water from leaking in and causing rust. I also ran silicon around the gap between the wood that replaced the rust out mangers to prevent hay/grain/dirt/water from entering the dressing room and causing the wood to decay and the walls to rust.
In this picture you can see some of the rust on the plug, as well as the housing conduit spliced into the trailer wiring harness. Yikes!!!! I think this was done when the axles were replaced on the trailer? The rest of the wiring appear to be original.