ALL of our dresses and costumes are designed or purchased with specific input from the choreographer and coach; they approve the design, and the material. We are fine with this, as that is part of the expertise we pay them for. Also, we figure that we are representing them on the ice when our skaters skate. They also have never guided us into an incorrect decision.
They have always respected out budget, and worked with us within it. Yes, we always have practice run thrus with all dresses before test or comps - which is good, as what works on the hanger may not work on the ice or under the lights. Gives time for adjustments. And yes, butt checks sure do happen ... always.
I would say of the 25 coaches at our rink ... 90% of them do the same thing with costumes. All of the competitive track skaters that I have ever encountered have had their coaches/choreos do their costuming.
With my DD now being on the judging panel, we have had confirmed what we have always known in terms of the effect that costuming has on the "impression" that the skater makes. No, there is not a mark for costuming in specific, but, it does affect the overall package that the skater puts on the ice.