...the water pan was engineered for a purpose.
My theory on the water pan is that it was designed to mitigate leaky fire boxes that allowed the temp to climb too high in the smoker. That, and the average guy cooking in his backyard doesn't want to have to monitor airflow and track smoker temperature. The water pan allows a set-it and forget-it approach, no matter how leaky or wide open you have the firebox vents.
My approach is that if my fire is getting too hot, it must be getting too much air. Too much air means a leak, so I find and plug/tape/seal the leak and regain control of the air intake. On the bullet smokers, there are only a handful of places air can get in, and they are all easy to seal. On my pro-q, i have two of the bottom dampers sealed shut and the doors taped. I found that without water in the pan, I could easily control and maintain low temps with just one vent.