There's no answer for this to be honest, but the best way to release an official build faster is to help test the development and beta builds
I am using build 687 which works great, but with later versions I always have that really annoying client freezing issue.
I haven't touched PocketMine for a month, so I guess I can't weigh in on stability. It seems like a lot of features were implemented and a lot of bugs fixed though.
Signs and chest both work fine in 687 at least as I can tell. but Im almost always in creative so I don't use chests.