I see your point, but doesn't Orochimaru have corrosive DNA (Takes over the host, strong life-force, strong chakra capable of allowing anyone who wields his chakra able to control 40 Edo-Tensei's at once)? It wouldn't be too far-fetched to say his DNA is needed for KABUTO (Not ALL people) to go into DSM. Juugo was used to CONSTANTLY absorb nature energy (So he wouldn't need to do it in battle), Karin was used for healing, Suigetsu was used for his water technique, S5 for their abilities. Plus Kabuto did state that his body; was Orochimaru's body. I think that says something.
Lmfao at your second point.