Let's take a step back. Who was complaining about the old GUI? No-one!

Good point.

M2C:


The blueprint dialog is fine. For me the preview part is NOT part of the dialog.
I like the old gray and minimal look a lot. Keep colors to the items themselfes. Maybe just refine it a bit. Avoid lines ...

*push*

I would love to monitor important stats on a second screen. (mainly power and logistics network, maybe also research)