you guys are getting confused. the body swapping ability is the immortality jutsu. all it is, is orchimaru's soul being put into another body from his current one. it basically keeps him from aging. the ripping off face deal isn't part of the immortality jutsu. but he is able to take the faces of the people he kills or that are already dead and able to mimick their voices. he is sick.

EDIT: lol, yes, this is a repeat. you must've posted when was in the process of it.