Know that 95% of the time the people that steal from you are friends, family or friends of friends and family. Not that this helps, just thought I would bring it up.
I leave my house unlocked at all times & keys in the truck.
If someone want's to take something of mine, theres not much I can do. Locks only keep out the honest ones, any lowlife crackhead that sets their eye on your property will do whatever it takes to deprive you of it.
I suggest an alternate battery cut off. They sell "switch over" selectors for turning on and off batteries in marine applications, this may deter the "more honest" theif who will only steal something you've made too easy to pass up.
Good Luck.