I built a cabinet a while back, I really am happy with it for what it does. I also debated between a reverse flow and direct, but ultimately decided a direct was much simpler and really turns out some great product. Let me know if you have any questions I'd be happy to help, it was a fun process!
Yea it was my own design, I did some looking online and then did some CAD work and some sketches so I knew what all my measurements would need to be and how much steel to order. I ordered the steel cut to size so that was critical.
I made some on the fly decisions as I was building for some of the smaller details that I didn't fully flesh out beforehand, like how the racks would be designed and function, how the charcoal basket would be suspended etc.
Since a direct flow is essentially like a drum smoker, you got a lot of room for wiggle. Reverse flows and gravity fed might require a bit more planning.