A conventional switch typically won't have a high enough current rating and would be rather large if it did. What I have seen folks do (I am also going to do this) is put a small auto fuse receptacle in the side or bottom of the plane and use a 30-50 amp blade type auto fuse as a fail safe switch. You just plug in the fuse to arm.
There is a thread somewhere here or on the other RC Groups forum that goes into detail. I will look for it....
This type of fuse: