In reply to Luke Cavanagh.

As a developer of a page builder theme that follows the same hybrid approach of Layers, I’d like to add my two cents opinion.
Separating theme versus plugin functionality is a smart rule and there are many (also commercial btw) totally legit reasons to want this, but there’s definitely a trade off. In our experience, integrating the page builder (which initially, in private beta stage, actually WAS a plugin) and the Theme, allowed to keep a lighter footprint and guarantee that things work out of the box much better.

As a silly example, knowing which grid CSS framework the Theme is based on, allows the Page Builder side to NOT have to load another one.

Of course there are trade-offs with both approaches, but personally I was fed up seeing so many sites built piling plugins on plugins, resulting in inferior performance and great sluggyness.
Some people rant about WordPress being slow, only because they run sites with such kind of “plugin-tower” approach – a “pervert” way to see software modularity.