Tongue jack's for the most part suck, go the extra and get a single foot type that cranks from the side like legs on a Big truck's trailer.
Go for brakes on BOTH axles as said.
D-rings on front, rear, and sides front and rear.
Lights protected from crash and bust incidents
get at least 5K axles, with 16" tires, You just don't have as good of a selection with 15" tires
Ramps, everyone has their preference, I like fold down's . If you get slide in's a nice set of aluminum ones will be a lot easier on your back.
If fold down, get channel straps to keep them in place, chains are noisy. Flat bar bends as ramps will walk to the inside.
Quality wiring in a big plus.
You may only need a 14' trailer, but a 16' with a 2' dove tail allows you more options to get your load so that it pulls good without swaying.
If you get a wood floor, look at how it's held down. A lot of trailer MFG'ers do not put enough hold down on them and when the wood dries, it rolls up.
If the boards are not treated, a good wood treatment will be needed, you can buy some or take the time and make your own. Used Motor oil and kerosene and many coats to let it seep in on a hot as hell day will do wonders to keep it from rotting. Seen it, done it.
Hudson's are a great trailer, but lil too narrow for my taste, depends on what you will haul and what you think you may need to haul.
A good mounted spare is nice, two is even better.
Storage box for straps, chains and so on is a necessity.
DOT reflective tape everywhere possible, that stuff is brighter when lights hit it, than the actual lights.
a header bar, to keep something from rolling off the front.
as said, a tag mount that will stand up. You will loose your tag at some point with the cheapie plastic ones.
Do not buy one made of angle, that's for lawn mowers and Suzuki's
all I can think of