Battery Switch - Pointers wanted.

I would like to install a battery switch, so my battery will not go dead in periods of "un-use".

The cable from the engine compartment to the battery is 0 gauge cable. Could i use 2 gauge in order to splice the switch into the line? Or will that cause a heat issue on the 2 gauge cable?

i should be switching the hot side, but would it hurt to switch the ground cable?

why not just use one of the many items made for this purpose that attach in place of the terminal? or just disconnect the battery terminal?

http://datashelf.com/bmw/b2.jpg