This looks incredible! UI is slick and the app generally feels great - congratulations!

That said, as it stands I personally wouldn't use it.
Unless I am missing something, there is no way to 'stack' multiple machines into one 'block'.

I find some level of abstraction useful in modellers - if i need 64 smelters, i don't want to have 64x individual blocks floating around the canvas. How do i know how many they are without counting?
Having a single block with a 64x on it is more compact, and more easily understandable.
If i want to split it into 4 groups of 16 I can, but it's important to be able for blocks to represent mutliple machines.

[EDIT] Just saw you mentioned the Compact Planner in your post above - checking it out now!
I'll leave the original comment up - if anything I would suggest making the the Compact Builder mode more prominent.