As someone opposed to cheating, I would not want an auto diamond pickaxe.
However, starting with a stone set of tools (either auto or via a stocked chest) would be acceptable, because the wooden stuff is a pointless waste of time.
Also acceptable, hiding diamond tools in hard to discover places - maybe even leaving obscure clues around the place so it's a treasure hunt.
(So long as the clues are challenging and you can't accidentally stumble upon one of the hiding places.)
If there's a way to create redstone combination locks?