In MESOS-1806, it mentions replacing ZK with ReplicatedLog or etcd. The replicated log is a mesos native construct, that has no external dependencies.

If you can replace ZK with a native Mesos construct, seems like it allows you to remove ZK entirely. I meant to say "optionally allow removing ZK as a dependency" in the original post. You're totally correct in that regard.

I do wonder why the GP would want to, given how ridiculously reliable zookeeper is.

Oh I love zookeeper and have no issues whatsoever with it. However, it is almost universally the first thing I hear people moan about when someone suggest they use Mesos. People don't like Zookeeper.