...

See the above and the Tao of ZooKeeper. We really want to keep ZooKeeper focused on its core mission and are averse to code stability and maintainability risks. If you do have an idea, don't lead with "i really want this and it is simple to add"; try to show that it helps zookeeper in general.

There is too object synchronization happening between threads

yes, particularly between PrepRP and FinalRP. See https://issues.apache.org/jira/browse/ZOOKEEPER-1092^{Image Added}