I think instead of a futile search for a "bot-proof" game, we should be thinking of a game/challenge that could be INTERESTING to solve through programming a bot, with many different possible approaches, where a "smarter" bot with fewer hardware/energy resources available could easily out-mine bots that have much more resources available but use more primitive approaches.
This game/challenge would also naturally grow in complexity over time in a manner that would make it difficult for bot designers to predict and quickly adjust to.
Ideally this game/challenge/problem would not even be something arbitrary but somehow contribute towards cutting edge AI and machine learning research in general. Which in turn would attract the world's leading researchers and the most talented programmers to work together in pushing the limit of machine intelligence.
How about that?
In general, I think this is a cool idea. Although, I see two problems (that may be solvable but need at least additional consideration from my point of view):
- I already wrote it above, and still believe it is true: Such problems, where the "actual goal" is to give cutting-edge research an order-of-magnitude advantage, is not suited to securing a network of transactions. I wouldn't want to run an exchange and accept a currency that could be 51%-attacked every time someone made a break-through. (HunterMinerCrafter stated himself above that he could 99% Motocoin if he wanted to. While trusting him not to do it is possible, I wouldn't want to have lots of money at stake with that. Then I could just put it into the bank, after all.) Having the currency "just for fun" and not intended/advertised as fully secure (as Motocoin's website still does) makes this point moot.
- While I'm all for promoting research (I'm on a research grant myself, although not related to AI or crypto-currencies but applied mathematics), I also think that results should benefit the community at large (keyword "Open Access publications", for instance). I doubt that the research done for bots on Motocoin or a similar currency would at all be published somehow, as it is in the botters' best interests to keep their results in secret. Why should the community of currency investors pay them for something they research just for their own profit?