Dave, I can say that, in all my smokes, I've never smoked 2 totally dissimilar meats at the same time. And, here's why...I'm pretty particular when it comes to how my finished meat turns out. When you try to smoke things that don't cook nearly the same, you introduce the possibility of a lot of error into the cook. Lots of folks do what you're talking about, but to me, it's unacceptable. Just my school of thought on it - no "right or wrong" way on the subject; just giving my 2¢.
If I need more than a pulled pork meal, or brisket, or ribs, etc..., I smoke them at different times, or one thing in the #1 and one thing in the #2 (I have the luxury of having 2). I rely on getting each individual smoke as good as it can be, and a repeatable method; adding different meats to that takes out the predictability, and adds unneeded stress to the cook, in my view. Definitely a "to each his own" thing, though!