So I'm a little confused. Why not just buy a weber kettle
rather than get an offset designed to grill burgers and steaks? It'd be massively cheaper and better suited for the job.
I understand your interest in a door at the end of the firebox but I dont think it's necessary. Plenty of air gets into the fire from the intake in the end of the box. And as noted the top door makes it easy to add charcoal and splits. It's 3/8" steel. It recovers quickly and holds heat very well.
Foldable smoke stack? I saw that on a Meat Church video. Mine doesn't leave it's parking spot so I don't need it.
As far as the tuning plate. I like it on my Bell Fab. It keeps the side closer to the firebox from getting en fuego. In my smoker it keeps the Temps roughly 25° cooler than the stack end. Perfectly acceptable for me on a stick burner.
I understand you're giving this purchase a very hard look. It's a lot of money. However, I can't count how many times I've walked out to check my fire and temps only to find them both be perfect. I then turn to my wife and say, "This thing is worth every single penny."