I'm still not convinced that this is meaningfully exploitable. Anyone care to demonstrate? 
How fast your bot can mine new blocks? Can it generate one block at least every few seconds? If so, just start to generate blocks right from the genesis block untill you will have more blocks then there are currently, then send all your newly mined blocks to the network, voila, and you will own all of motocoins except for my premine. This is just a 51% attack.No it is not a 51% attack because it is not involve much resources to accomplish. Because in motocoin threshold value is not linked to block issue time attacker can produce blocks whose solution is stupid and slow.
It is like producing a blockchain for bitcoin where eachblock have only one leading zero. This is not a 51% attack by definition because attacker can have far less resources than the rest of the net. He only shall be able to form blocks fast enough.