What about someone like Kabutomaru or Jugo? Kabuto and Jugo have the ability to absorb natural chakra by just standing there which means their reserves and power would probably be topped off every couple moments in their cases. Jugo is just a force to be reckoned with and is somewhat intelligent while Kabuto contains the DNA of all Sound 4, Suigetsu, Jugo and Karin(?)
That combined with his vast intelligence and knowledge of the human body AND his chakra scalpels which have been shown to cut through flesh and wood (he bifurcates Itachi). He shouldn't have any problem getting through the worlds. Any comments on this?