?
Chocolately packages are, essentially, nothing more than a powershell script that downloads and runs an installer from some url on the internet. It would be virtually impossible to inspect arbitrary powershell scripts and determine what they would download when run, and then download/proxy those installers.
So, if you want full control over all aspects of the chocolatey packages (including the installers that are downloaded), you will just have to create your own based on the contents of the open-source packages.