Beside the usual things, ac/heat, Gen compartment, 16" tires, etc. The stuff that is generally in every trailer.

These are things I will have in my next trailer the end of this year. LED lighting everywhere(as much 12 volt as possiblwe) to including outside. Wheel well cabinets, a fold down table. TV/Monitor and sound system inside and out. As much cabinetry as you can fit in the trailer, overhead and base cabinets as well as overhead on opposite side of wheelwell cabinet. Storage for things like ratchet straps, portable awnings, chairs, oil etc, I like having a closet to hang my gear, a winch compartment either under cabinet or in floor, and a toolbox under the counter top. Extended rear ramp to ease loading and unloading. Rear loading lights. Plumbed for air outside and inside and room for under cabinet compressor. 35 or 50 amp service for shore power. As large and inverter as I needed. Think that's most of it. Id like to have a good awning that attached to trailer and storage for that too, get tired of the portables.