A "switch blade" is a knife that comes out by button or centripetal force. You could probably come out with a design in five minutes.
A reverse blade works at the needs of plot. It doesn't exist in any traditional fighting style for the single reason that it isn't useful in fighting. It is madness to have the side you use for impact dull while weakening the back side of the blade, which takes the stress in combat. It was invented for Kenshin because the author needed him to go up against real blades (so it couldn't be a bokken) and always have the temptation to turn the blade and kill (eliminating the Iaito), while symbolizing his oath to never slay another human again.
Therefore, the reverse blade can do what the author says it can do; nothing more, nothing less.
[This message has been edited by Benjamin1986 (edited 01-29-2005).]