Well, if you used the stock type of control valve that Lynn was talking about to regulate the temp, then an emergency shut off valve in the other side should do the trick??

How often do heater hoses and cores rupture inside the passenger compartment of cars anyway?   If you were going to try and isolate the entire hose/core system, you would have to install valves in the engine block and water pump housing.  That is not impossible, but difficult in my installation.

Bill B