In principal, new van, “minimalist” build.
We all define minimalist personally. How you travel, what you do with the van influences your definition too.
If someone else is doing the work, you may be underestimating the labor bill, unless you are letting them build what they have built for other vans. These projects tend to eat up a lot of time.
We travel in our “minimalist” camper as long as 4 months at a a time, but supplement boondocking with state/national/county parks and hotels, where we use showers, laundry, wait out extreme weather, etc. We rarely stay in a single camp more than 3 nights, but when we do, it is usually for 2 weeks (maximum allowed). These camps are at the beach, with facilities.
Our outfit is our 4th RV, so we have refined the camp to suit our needs. We went from backpacks to car camping, to pickup camper, to massive travel trailer, to midsized Class C, to a van with a galley with ice chest, microwave, butane and electric burner, propane and electric heaters, 5 gallon bucket potty, 100 amp battery, lots of storage for the scooters, SUPs, canoe, gifts for the family. And yes, insulated to the gills, even all doors, headliner, floor, etc.
I use this van to haul when at home, so it breaks down to walls and floor and goes to work.
The new build will be similar with 200 amps of battery and an inverter- very posh for us.