less van life and more boondocking around North Wales in an old mk2 Volvo V70, it's not perfect but I get by pretty well.
I mainly use it for fishing but you can get set up pretty comfy in most places, you can even rig up a milsurp poncho over the top from the roof bars with bungees to make a decent side shelter. It's needed no work really to do other than having the get up and go to get out in it. The only thing really I can say I've bought for it (and in fairness it's been amazing levels of win) is a 12v coolbox. I wouldn't mind getting decent roll up solar panel to keep the coolbox running when the engine is off and to keep my power bank and tablet topped up (I like to settle down with a movie before going to sleep at night)
I've got a bag with spare clothing/hygiene supplies in, a couple of 2ltr water bottles (which I want to replace with a jerry can this month) a bit of easy to prepare standard (canned/pasta/packets etc) food and a load of 3-in-1 coffees. The cooler has a 6 pk of pop, a 3 pk of 200ml uht milk (I like my breakfast cereal in the mornings) I keep a folding BBQ (doubles as sweet fire pit) and couple of bags if instant light charcoal too at this time of year. The back seat is wide enough to take my beach tripod with room to spare and rods in travel quivers
To sleep on I've got a 10mm foam mat under a 50mm self inflator so it's plenty comfy. I keep a woobie and big wool blanket in the back for at night but have never need more than the woobie unless it was snowing.
The car has a pop out roller which runs from the backseat headrests to the boot to cover stuff up so it's hard to tell it's anything other than car when I'm not set up.
With what I keep in my daypack, as long as I'm topped up on stuff like stove gas, my meds, water and maybe bait you could comfortably spend as much time as you'd want in it.
In July the test will be running it in 2 person mode on a trip to Mousehole with th' wife
>>1280514pic and details for your connivance