Bear in mind that the process of adding a water pan would require that you design a pit to have enough BTU capacity to overcome the cooling effect of the steam coming off of the the water pan. And that would complicate the beautiful simplicity of the design of the PBC. And, I doubt that you will ever make anything in a PBC that is "dry"....
In other words...I don't think you would be happy with the results of adding a pan to a PBC. It just is not designed for that. But - the good news is - there are other ways to get the effects you may be seeking:
1. Injection - always a winner if the goal is to infuse specific flavors and to a lesser degree - aromas. Make whatever concoction you like - allow the ingredients to steep, or simmer them then
chill the material to be injected to 40 degrees F or lower BEFORE use. Let's be safe here 
Now - there are some products that you want to use caution before injecting. Chief among them would be pineapple juice. Boil it first. If you don't - the enzyme in Pineapple juice called papain will break down the muscle fibers in meats if left uncooked for more than a couple of hours.
2.Brining or marinating - a more time consuming way to use the osmotic principles of fluid exchange between the ingredients in the brine or marinade - with those native to the meat. TIP: Brines really only work well if the given meat ( usually turkey or chicken in this case) has NOT been pre-brined by the facility that packaged the meat. Read the label's fine print to ascertain whether this is the case with what you are buying. As a general rule - when buying poultry at a typical grocery store - the birds are pre-brined unless noted otherwise.
Please observe the same chilling temperature rules of keeping the Brine @ 40F or lower during the brining process.Here is a link to some brining ideas:
http://www.letstalkbbq.com/index.php?board=30.0
