Re: Costumes designed for stage performance - it's not about looking inferior close up. You don't see this as much at anime cons, granted, but at some of the ICG events, I have seen costumes that were actually multi-stage affairs, things that look at first glance to be quite normal until the moment on stage where the costumer reveals the other part of the piece. Cloaks that turn into wings or sunset skies, for example, or other pieces that transform. This sort of transformative costume is not the kind of thing that's best displayed in a hall setting.
Speaking from my own experience, when I wore the Fairy Park Statue onstage, I was on a pedestal to provide extra dramatic height and look more like a statue - and the extra height allowed the Statue to "crumble" at the end of the skit, because the wings collapsed around me as I "fell" and they would not have cleared the ground if I hadn't had that extra height boost. I did try wearing the costume in the halls later - but the overall look just wasn't as effective without the pedestal. In fact, because of the way the costume was designed, I looked shrunken, shorter than I actually am. So in some cases, there really are design cues that one makes intending all along for them to be a critical part of a stage performance.