I understand why teh costume change, as she was no longer part of Vector. It makes sense for her to ditch the Uniform, but yeah. The choices for later uniforms were a bit... Odd.
I don't think I ever hated Shion, but really she was one of the weaker characters. She left no where near the imperessions that Kos-Mos, Chaos, Jr., Ziggy, or Jin leave.