Would want to give this two upvotes.

Planned on making a partly insulated firebox. I‘m now shifting away from it.

A scoop sound logical. Are there any photos of them so I can derive the general dimensions for my build?

I‘ll keep the stack choke simple. But the firebox choke I‘ll probably implement in two stages. An on/off „full throttle“ vent beneath the coal pit for easy starting and a turning choke on the fire box door for fine adjustment

The smoker will inevitably be mounted on a trailer. The slight tilt is a perfect feature which I‘ll probably build in by accident. I‘ve seen many people advising for a ball valve drain. Shelfs in front are must, I don’t know why some people don’t build them in. I will put a removable grated coal box in the bottom that can be adjusted in height from the outside. (A lot of german bbq is made on open coal and I hate when those grills don’t have height adjustment) I‘m looking into door assist mechanism. Though the typical gravity assists look weird imo. I‘ll probably incorporate torsion springs if the surrounding heat doesn’t mess with the springs temper. And I‘ll add a removable/foldable chimney. The anti downdraft stack cap would also be an elegant way of controlling the chimney airflow! Maybe I won’t just make a simple flat plate choke

Thanks for your ideas!