it wouldnt work. you have to think more advanced about it.
your mule should and will only stay in safe-zones near the guards to be always safe. if i as a mule attack my farmer the guards will instantly kill me. and i will lose all items (they will drop on the ground for everyone to see) ...
Well look at this crap, you're not allowed to trade an item for 1 week lol. and mules will have a hard time..
literally impossible to farm gold
Read more:
https://www.reddit.com/r/2007scape/comments/3oysmi/deadman_mode_mules/