If you want to get exotic about trailer brake systems, you could go with electric over hydraulic brakes. These are a more recent development in the trailer industry, at least as applied to boat trailers.
As I understand it, in this system, a braking control module incorporated into the vehicle's tow package system provides proportional electrical signals to the trailer. The trailer has an electric motor driven hydraulic system that actually powers the brakes.
The advantages here are that you get
1. proportional braking that is controllable and adjustable from the cab.
2. no braking going downhill, unless you want it (unlike surge brakes).
3. no problems with backing up (again, like surge brakes that lock up when you try to back up, necessitating a solenoid or mechanical lock out system).
4. plenty of hydraulic pressure to power double or triple axle drum or disc brakes.
On the down side, to have an effective break away system, the trailer has to also carry a small battery to power the system should the trailer become disconnected from the tow vehicle.
I looked quickly to find a good article to describe this system, but no single easy source. If I find one, I'll come back and post it here.
C-Bill has such a system on his trailer, and I saw it at Lake Shasta last year, but at the time, I was so unfamiliar with the system that it kind of went by without my fully appreciating it's advantages.
Another good addition is Kodiak brand stainless disc brakes. I added Tie-Down stainless discs on my trailer last spring and haven't had any problems with them, but the difference between the two brands is like the difference between the houses made of wood and bricks by the little pigs! The straw house, of course, is the drum brakes of ordinary steel.
Get the discs on all axles. Think about even an aluminum trailer with stainless fasteners if you're a salt water weekend warrior without easy access to rinse water.
I've got my first roller trailer that came with my boat (used), and it definitely has it's advantages in various difficult to launch conditions, such as shallow water. Otherwise, not a problem, and works fine.
A strong and tall set of guide-ons is one of the best launching aids you can have on a trailer. Centers the boat at the ramp in wind and currents, and keeps it centered when trailering. Wimpy ones are proportionately dysfunctional.
Does anyone use a power winch to any advantage on a boat the size of a C-Dory?
An absolute great addition would be a ladder built onto the trailer tongue to get up and over the bow and pulpit upon launching and retrieving. Have one on my pontoon boat and couldn't do without it!
Cover the front "V" section of the trailer with 1/2 " waterproofed plywood to be able to walk out on the trailer when necessary. Add non-skid to the tongue and widen the tongue with plywood or metal if necessary to provide a safe walking surface to walk out on. Non-skid on the fenders helps a lot.
Get a 45 degree spare tire mount and use it to place the spare in such a way that the tire becomes a step between the dock and the trailer.
Most new trailers come with the cheapest wiring possible to keep the cost down. When you have to re-do the system, throw out the old system and
use good, high quality covered tinned cable, LED lights. and make all connections above the water level if possible. Add a junction/distribution box on the tongue under the winch to make secure and above the water line the connections between the front pigtail/plug and the wires to the light fixtures. Get the highest quality solderless connectors, then paint them with liquid electrical tape, then cover them with shrink tubing to prevent abrasion. Ground everything necessary both through the trailer frame and with ground wires. Bad grounds are more often the problem than anything else after a few years. Eliminate points of possible abrasion for wiring.
Get the trailer tow package with a new tow vehicle. Better electrical connections, gear ratios, cooling, brakes, suspension, etc. Also includes trailer brake module for electric brakes, etc.
Enough from me. HTH. Joe.