For me the "black and brown" issue is probably better summarized as a general rule of thumb I try to follow - don't mix two colors which are too close in shade. The examples you posted show black with various mid-range browns, which is actually fine to me... it's just the very dark browns against black that bug me. Same thing goes for navy and black actually - blue and black can look great together, I particularly like it on Starkiller's TFU2 training robes:
In that case as well you can see where the contrast is there. For me it's all about contrast, really makes the different colors of the outfit pop. Just personal preference again.
I am sorry. I just find that a discussion of "Fashion" dealing with color choice coming up with people who enjoy dressing like a hybrid of a samurai, massage therapist and a gregorian monk with a flashlight hanging from one's belt is a bit silly.
From a fashion point of view, there are far greater crimes we commit than wearing brown with black.
Unless you are trying to re-create another character, all this stuff is subjective.
Getting measured today!!! Next step: fabric selection. I love the fact that the person making this is local (we work for the same company). This way I actually get to go fabric shopping with her.
Choose your fabrics well. That is the most important part getting a garment made.
Good luck! I can't wait to see it.