Changing Mac Installl Packages to include drivers that default to duplex printing

How to change Mac installation .dmg packages to default to duplex printing

There is a way, but it's driver dependent.  You can change it by opening the .ppd file from the .dmg.  This builds on the answer below. How to create a Customized Pharos Uniprint Popup Package for macOS

Once that package has been built, you would change the .ppd file, as long as the option is there inside the driver, to accomodate duplex printing by default.

Here's an excerpt from http://www.cups.org/doc-1.1/sum.html#2_1

Printing On Both Sides of the Paper

The -o sides=two-sided-short-edge and -o sides=two-sided-long-edge options will enable duplexing on the printer, if the printer supports it. The -o sides=two-sided-short-edge option is suitable for landscape pages, while the -o sides=two-sided-long-edge option is suitable for portrait pages:

lp -o sides=two-sided-short-edge filename ENTER
lp -o sides=two-sided-long-edge filename ENTER
lpr -o sides=two-sided-long-edge filename ENTER
The default is to print single-sided:

lp -o sides=one-sided filename ENTER
lpr -o sides=one-sided filename ENTER