I'm coming a little late to the party but put me down for using the widest trailer deck you can get, either 8' or 8'6" (if legal in your state).
As for your axles, 3500# axles from Dexter cost about $60 more to add the parking brake feature. Throw in around $200 or a bit more for cables, equalizer and handle for one axle, a bit more for two axles, and you will never have to worry about wheel chocks again. I prefer two brake handles, one for each side as it allows one person to pivot the trailer to align it where desired, pivot it on an uneven slope to better level it side-to-side or to align with a hitch. As an added bonus, most trailer brake handles can accept a padlock with no more than a hole drilled in the frame of the handle.
I know some of this has been covered but....Sway while towing is most often caused by the trailer center of gravity being too far aft. Typically, you want 10-15 percent of a bumper hitched trailer's loaded weight on the hitch (usually closer to 10%). If that causes the rear of your tow rig to settle too much then plan on a load equalizing hitch.
What you are shooting for is for the relative wheel well height of the tow rig to be the same with or without the trailer hooked up. If you measure the heights of your front and rear wheel wells with a normally loaded tow rig and then hook the trailer up you should aim to still have the same height difference as too much weight on the tongue leads to low weight on the front axle and sloppy steering (the equalizing hitch will help with that).
You'll want some way to heat wash water even if it's for just hand washing. If washing and utensils or pots you'll need a thee bay sink.
Plan your electrical system early enough to at least have an idea where you'll be running your conduit, convenience receptacles (permanent appliances like a cooler need designated stand-alone circuits), light and switches etc. Keep the ability to clean and sanitize them in mind. Exposed conduit and boxes above a counter would be hard to clean and sanitize..... And plan you shore power or generator hook up early. If using an on-board generator decide how to vent the exhaust early enough that you aren't putting a hot exhaust pipe where it is a hazard or the outlet in an unsafe location for fumes.Good luck and please keep us informed. This is likely a build I will only ever be able to watch and will never build myself so I'm coming along for the ride....