I don't know if anyone has considered this before, but is it possible that Yoruichi not having her zanpakuto and being able to turn into a cat are related? Due to her personality, I can see her having a feline zanpakuto something similar to Rangiku and Haineko. We know that Kisuke created the hogyoku to eliminate the division between shinigami and hollow, so why wouldn't he use his good friend Yoruichi in an experiment to increase the closeness of shinigami and zanpakuto spirit? So it happened, but went horribly wrong and the two melded. Now Yoruichi has the advanced capabilities of a shinigami/zanpakuto hybrid with a cat transformation. It makes sense doesn't it?
it could be possible. remember we dont know what went on during the 110 years since they began living in the world of the living. who knows, they probably even had strong intimate relations during that time for all we know. so yes i think that is a strong possibility. no wonder she doesnt carry her sword around anymore.