Assuming you already have an air compressor going in? My new trailer has a 25' fuel hose reel and 50' air hose real in the same box accessible from the outside / near front of trailer.
If you always like running a genny then solar is a non-issue, but with that said I had solar on my last trailer and loved it (never had to plug it in or worry about it) so I am in the process of adding all of that to my new to me trailer (keep in mind if you go this route you need an inverter etc
you putting in plenty of cabinets and a big tool box?
I will be moving my spare tire to be mounted hopefully underneath the very back of the trailer.
new trailer has a small sink in the work bench which drains straight under the trailer... definitely excited about this since I always need to wash my hand when loading / unloading / working on stuff and beats having to get the motorhome sinks dirty / waste grey tank capacity.
new trailer has 190 gallons of water which is overkill lol... only 60 gallons of fuel, but I would like to add another 40-50 gallon if possible.
escape doors are awesome to have