schematics is OK as an outline, but:
1.It represents all you needed in 1975 for electricals in a small trailer. Me thinks that a 2014 rewire would include more circuits for more AC loads and lots of DC circuits for stuff like inverters, multiple DC accessory outlets, a digital meter for battery
monitoring and lots of wiring for additional LED lights
. And ferget the 120 volt fluorescent fixture, it's soooo last century.
2. The electric brake wiring is not only outdated, it is illegal in most states as it does not show a break-away switch or power supply for same as is generally required for trailer of this weight
. And even if not "required", it can be a life saver.
And you may only want lighting
on the DC side today, but in the future you may want to add stuff that's not yet even invented, so wire wisely and provide extra circuits for future needs. BTW: Most 12 volt USB charging adapters do not like line noise that can occur when using multiple ground points. Been there, done that, and on a dinky pop-up tent trailer at that.
And Last... As it wasn't yet answered; if you are starting from scratch I would suggest mounting your power chassis as close as possible to the battery. If the battery is on the tongue, under the front bench would be a good location.