I thought the problem with darkcoin is the centralization of masternodes. It costs 1000DRK to run a masternode. With darkcoin at at $2.83 thats $2,830 required to run a masternode. It's currently at an even higher price than that! If it reaches $100 then that will be $100,000 to run a masternode. Impossible for almost everyone, resulting in centralised mixing services at severely reduced (or completely broken) anonymity. Anyone care to explain why I'm wrong?
Most of us anticipate that in the future some sort of trustless masternode share program will be implemented. Barring that, an even easier fix would be to lower the cost of a masternode to 100 DASH, for instance. In your scenario, that would reduce the cost of a masternode to $10,000.
Another improvement that is planned is called masternode blinding. Basically, this will prevent your masternode from seeing where the present inputs came from. Consequently, even if you did own the vast majority of all masternodes, you still wouldn't know which node a mixing transaction came from, and couldn't track it backward or forward.