Your trailer usage will be similar to mine. I live a half hour from my field. The trailer store my models, giving me more room in my shop.

I have a 110V charger in the trailer, power is supplied via and extension cord, running to the trailer from the shop. The shop's wiring has ground fault protection, but I put in a ground fault outlet in the trailer, too.

The ability to charge from the tow vehicle takes about a half hour to wire up. It's nice, but not necessary.

Most of what you need should be available at camper supply houses. The rest at discount stores, like Home Depot, or Lowe's.

My inverter is mounted in my flight box. It's an inexpensive unit. Sorry, I don't know the specs. My neighbor "loaned" it to me, and won't take any $$$$ for it, or take it back !

Have you considered ventilation ? My neighbor installed a covered roof vent, purchased at the RV supply house. I put in 2 side vents, near the floor, that I bought from my trailer dealership. The combination of vents helps to keep air moving inside the trail, when it's closed up.