I think an important aspect about this game is the satisfaction, and dopamine hit, of making very compact builds.
I've consistently come into situations where a build could be considerably more compact, if i could somehow utilize that one (usually building exit) tile and send the product "sideways", to be processed by a different branch. I'm talking specifically about the tunnel entry, not the exits.

A few "tools" like this, could increase the ability to be creative, allowing in greater design diversity in areas where one is limited by rivers/edges/other buildings.