good luck on a switch to prevent theft. a hot wire from coil to battery defeats that.
unless you physically remove parts.. I can start your tractor.
if I can't start your tractor.. I can probably laod it on a trailer with a wich.. ir a pocket knife using it's own battery to roll her.
or If i really want it. i can cut your fence and let your animals out and use a roll back.
best of luck on securing a tractor.