That sounds like something I've been fantasizing about if I ever win the lottery!
* Triple 6000 lb axles w/16" tires - 15" tires blow out too much and main reason for triple axles is that if your in an area where you can't pull off to change a flat/blown tire, the 2 remaining tires will help support the trailer without being overloaded by the time you find a spot. (Of course triple axles will be tough your on the wallet if you travel over toll roads a lot.)
* Dual halogen lights outside.
* Dual electrical outlets outside & multiple interior. (Box fan, battery charger, etc.)
* Generator/box.
* Dual in-floor spare tire storage. Good for tool storage too even if you dont carry 2 trailer spares.
* I've been thinking that a roof hatch in the riser area might come in handy some day.
* As much storage cabinets and wall racks as possible.
* High wall slick mounts.
* Iffy on a winch. I carry a few good come-a-longs.
* Escape door properly positioned for full car door opening clearance.
* I think the rubber "coin" floor is more durable than vinyl flooring.
* Diamond plate rectangles positioned for each tire. (Possibly raised if needed to help the door clear, but you can only go so far if the car is low.)
* Overhang or big drip rail above the ramp door to minimize rain from getting in the door seams and possibly latch mechanisms. (Had a hinge support area rust out because water got inside the ramp.)
* Heat/A/C.
* Had an awning on my 28' tag, but it was a pain & was removed after it got damaged.
* Always get a little more length than what you "think" you'll need.
Probably more ideas if I had time to check out more options.
Post pics when you get it!