I like the tool mount idea, ax, shovel, machete.
The door mount would have more room for tools, but your front fender mount could also be used to mount tools and straps as well.
An ammo can (depending on whats in it) or Rubican/Rotopax might be a little heavy for swing weight opening the door. Still a good idea.
I can see it would mount to the hinges but how would it mount to the other side of the door without drilling and bolting?