hi Keith,
We definitely plan on having an offline process, and welcome your feedback on it.
You can read a bit about how the hub works (it's in beta, so please forgive the rough docs). Specifically, check out "Configuration and Offline Installs":
https://inedo.com/support/documentation/proget/installation/hub/inedo-hub
The Inedo Hub wraps Romp (more coming soon on that), so you could also use that to install ProGet as well, as a command line process.
Does that help?