You have not proven to me that masternodes alone can help guarantee the integrity of the public ledger. I don't think they can. Only hashing mathematics can do that...
Replace 1000 Mh/s of consensus voting power of a GPU farm with 1000 DRK of consensus voting power of a masternode and you have your proof.
Darkcoin will be called FEDcoin or ELITISTcoin, since it doesn't treat individual newcomers the same way it treats its wealthy members.
As I said in the darkcointalk thread. It's basic psychology.
Nobody wants to make rich people even more richer.
Now this is the first and only reasonable argument I've seen for not getting rid of PoW mining. Took quite a many posts until the the real reason emerged.
Masternode owners wanting to be the greedy elite by getting rid of the miners is not exactly true, consider the following: If I'm a "smug" masternode owner getting 20% (= ~1 DRK/day), and the percentage is upped to 40% which results in there being double the masternodes there are now, I would still get ~1 DRK/day with double the variance. Not that good of a proposition from a selfish perspective.