Rolling checkpoints do not centralize control of the chain, they are a feature of decentralized consensus, what makes them evil in your eyes?
An empty private key may have no value to someone. The problem is you need to obtain a lot of them, the longer you wait the more spread and larger is the hashing stake protecting the network, making your task more arduous, and this is only one challenge you face. I illustrated the other challenges in the preceding posts.
Here is a fun thought experiment: why not issue rolling checkpoints at every block?
Any attacker only needs to get 33% of the stake from historical private keys; imagine the temptation for someone offering to buy them all together for some thousand dollars? All they need do is transfer their existing stake to new accounts at roughly the same time, and bingo.