First mods on my 2013 lacrosse 318bhs...
1. Added a battery disconnect switch to the top of the battery box, no need to run down the batteries in storage.
2. Added a charger hardness so I can keep my battery minder connected to the battery without keeping the trailer powered or opening the battery box.
3. Plug saver! The best thing I've every put on a trailer and I put it on every trailer I've owned and have never had a 7 way plug end go bad.
4. A bunch of clear tubs to organize the gear.
5. Key rack just inside the door.
6. Atomic clock ... But got to figure out where to hang it.