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?
I've been really impressed by what people have done so far, and no offence to anyone else at all, but Kev's Dumo thing is just jaw dropping. I LLLLLLL'd all the way up to the top and then all the way down to the bottom :'D