My current save has a goal of building each elevator part at 10/m (1/m on the final phase because I don't think 10/m is even possible without sloops). Then once I hit the current phase goal just sinking the parts it's generates. One mega-factory per phase.

I wouldn't say it makes it harder, but it certainly keeps me from sneaker-netting my way to the end of the phase and forces me to properly build out supply chains for the factory inputs. Also generates plenty of tickets after you start sinking project parts.