Will be interesting to see how all the different plugins that extend the current editor will work with this like I would imagine that is the key part of it will be focusing on getting the simple parts working really well and not a lot of functionality but being easily customisable for other developers to build on it otherwise everyone is going to just compare existing page builders. Example Robert mentioning columns wondering if they will implement in this or this will be easy enough to have plugins extend them.

Probably be a good idea after this progresses to a beta plugin that some useful extending plugins are created to work with it.