In case anybody finds this thread and is wondering the same thing, I just wanted to post an update (and wow, it's been more than a year!)
I ended up hatching Orpingtons and Barnevelders and raising them together. They are all 5 months old now and get along great! I've had no drama or problems whatsoever, even while I still had all the males. The Orpingtons seem to be dominant over the Barnevelders, but not overly so, and it mostly shows in the way they muscle their way to the food, the fluffy gluttons. Or maybe because at this point the Orpingtons are almost twice the size of the Barnevelders and just have a size advantage. The Barnevelders seem more timid overall, while the Orpingtons are curious and brave, the first to explore anything new.
One interesting thing I noticed is that each breed/color seem to be able to tell their own kind from the rest, even though I have 3 different varieties of Orpington. All the chickens get along well, but I noticed that the Barnevelders tend to hang out with each other more than with the Orps, and they like to sleep next to each other. The Orps stick together, too, and even group themselves by color. I'm used to seeing mixed flocks looking "mixed", or maybe I just wasn't paying attention before, but these chickens definitely seem to prefer the company of those who look like themselves.
Both breeds are very calm and docile, but the Orpingtons are WAY friendlier with people than the Barnevelders, even though all were hatched and hand-raised by the whole family, very socialized and very spoiled. The Barnevelders definitely don't like being touched and will avoid being caught, though if I really wanted to, I could still catch them easily (they don't like it, but won't run for their lives or put up an actual fight). They do, however, enjoy our company on their own terms. They'll come over and sit next to me, or preen themselves right next to me, or even perch in my lap or on my back, just as long as they do it on their own, without being picked up. The Orpingtons, on the other hand, are total puppies and even let my young children (clumsily) pick them up and carry them around. They like to be near me, next to me and on me, and I just can't get enough of them! I got three colors (Lemon Cuckoo, Silver Laced, and Red Partridge) and they are all like that. They are my favorite breed!
If anybody out there wants to get Orpingtons and Barnevelders together, go right ahead! They make great flock-mates.
Here are four of the girls: