It should be possible to install Cygwin, and then package that install in such a way that we can do a more silent install that doesn't require packages to be downloaded.

Some clues can be found here: https://cygwin.com/ml/cygwin/2010-03/msg00877.html

The fix should modify the bundle build to download packages into temp folder and then zip them. This zip then included into bundle installer.

c:\DevelopmentSuite\cygwin\setup-x86_64.exe -D --no-admin --quiet-mode --only-site -l c:\DevelopmentSuite\cygwin\packages --site http://mirrors.xmission.com/cygwin --categories Base --packages openssh,rsync --root c:\DevelopmentSuite

Another modification should be done to cygwin installer to check for included zip with packages, unpack it and do installation from local folder instead

c:\DevelopmentSuite\cygwin\setup-x86_64.exe --no-admin --quiet-mode -L -l c:\DevelopmentSuite\cygwin\packages --categories Base --packages openssh,rsync --root c:\DevelopmentSuite\cygwin