Whether you pull the fuse or put in a switch, it is still effectively doing the same thing but with a switch you don't have to physically get under the bonnet to pull out a fuse every time you want to put it into rear wheel drive......
Constantly switching to rear wheel drive will eventually (probably sooner rather than later) kill your transfer case.
The only way to effectively put the car into rear wheel drive without having any major adverse affects is to remove the front drive shaft. Probably not the easiest way to go about it, especially if you intend to do it frequently, but the safest none the less.