I just went thru the process of building a wish list and ordering a trailer 2 years ago.

#1 on my list was 16" wheels with load range E tires.

Further, in no particular order:

28 foot tag. That's a 28' box, plus the tongue. Not too big, not too small.

Spread axle, supposed to be more stable.

All aluminum construction to save weight and so it won't rust.

12000 GVW (2 6000 pound axles) to get bigger brakes, and because one of my cars weighs #5500. I don't like to push the limit on weight rating.

Large escape door, positioned low enuff to allow the drivers door to open. Properly positioned fore and aft to accommodate all my different cars where they would be tied down. I did lots of measuring and specifying to get it right.

Lots of E-track to tie down a variety of car sizes, plus plenty of cargo in the front.

Extended tongue to reach under the overhang of my pickup camper.

Tubular aluminum roof joists, not hat channel. The hat channel on my last trailer collapsed under snow, destroying the trailer.

12 volt LED interior lighting, plus 110 volt 45 degree florescent fixtures in the ceiling/wall corners.

Aluminum plate attached to the ramp door that covers the joint between the floor and the door, so junk doesn't accumulate in there, and so little wheels Like on wheel dollys or floor jacks) don't fall into the gap.

Spare tire compartment. in the floor. Not for the spare though, because I don't want to unload the cargo if I get a flat. It is for storing seldom used stuff. Then a spare tire bracket on the wall.

I wanted spring hinges to raise the ramp door instead of cables, but Lighting trailers does not offer that, and I chose Lightning for having the best price and good quality for the trailer I wanted. I also wanted cabinets, but maxed out my budget at the time, so I can add those later.

I didn't get a generator compartment because I have a generator built into the camper.

Good luck, have fun, get it how you want it, don't let the dealers bs you.