You are talking about something similar to what Unity3D does with it's "Active" boolean, right?
Maybe put return right at the beginning of your function(s) that you to not be executed and see if that works? You could combine it with the above like this:
extends Node
export (bool) var enabled = true
func _ready():
if enabled == false:
return
"Other code here"
func _process(delta):
if enabled == false:
return
"Other code here"
"Add the same two lines all of the other functions you want to disable"
Other than that I'm not sure there is a way to disable a script without clearing/removing the script from the node (though I could be wrong)
