I didn't read the entire thread but here's my .02 cents. There's no such thing as the perfect camper, as they're all full of compromises. For me, I had a 2002 Kamparoo Weekender for 14 years, then switched to a 2014 Adrenaline Rush camper five years ago. They're both the same style of popup campers, with 7'+ head room, and a large vestibule for dog beds, pack n play or adult cots. My Adrenaline has hot water, Espar diesel heater, an outdoor kitchen, a ginormous tongue box, add a room x2, can go anywhere, and haul all kinds of crap on its back. On a strong windy day, the canvas will flap and that's my biggest complaint. Brand new, these thing were less than $20k and were built in Montrose, CO, but they've been closed down for many years now. Kamparoo and similar style of campers can be had more easily as they're still being manufactured.
Before I bought the Kampaoo, back in '07, I thought about building my own camper. When the spreadsheet total sum number gave me a solid reality check, I started to look at the second hand market for my camper. While my time is not free, I can easily fabricate a camper but it'll take a solid year or more of trail/error process. Meanwhile, my child is staring at me and going "when are we going camping?". I wanted to make memories from the get go with a turn key package so that's the route I chose and have ZERO regrets.
I suggest starting out with an affordable camper platform, then improve it and make it your own. You get to tinker AND make memories with the family. Starting from scratch sounds great in the ideal world but rarely does this work out for most DIYers.
Now that my GF and I are empty nesters, we often take her 2013 Casita 17' camper more than mine. Hers has every freaking thing and I installed a Chinese diesel heater. Guess what, I have to replace the fuel pump on that heater as it lasted just one season, but hey, you get what you paid for. Her Casita has a 4" lift, which is plain silly and I'll take it down to 2" because it pogo sticks like mad!! When she splurges on the "shock absorber retrofit kit" for it, I'll install it. I had her replace the foam with a high quality foam custom cut from a local foam/fabric supplier. She sleeps better in the camper than in her own bed!!
Again, just my .02 cents worth.