To solve your problem with with google-chrome
you can add a dependencie with chromium-browser
which is in the repository.
I don't think it's possibile to automatically add another repository to met the dependencies of your package. You could add the requested dependencie in your package (if it fits) or fail the installation explaning to the user what repository to add and how to add it.
A good How to install it
guide on your package web-site for example.