I'm not sure I understand the whole "who will be center" discussion. Doesn't Ruby HAVE TO be it? She wanted to be the new super star in the vein of her mother and idol. I never entertained anyone else but her. If she's just a side-girl within the new B Komachi, then how she's gonna achieve her goal?
Similarity: They all know what failure/defeat is. (plus, they're hot, lol)