Alana, I tested the change and it is working for me with version 5.0.8. Ship it! :)

What you described should work; the connection should be proxied through the agent server you selected. however, I see you also submitted a ticket... so we'll review via that!

In ProGet v4.2, there is an option right under Disk Path that says Package Store.

This is possible using the SDK if you implement a custom package store (to allow ProGet to index packages stored in s3 and to allow it to push packages there), and an OData adapter to alter the package download URL sent back to clients. Our Creating a Custom Package Store tutorial is out of date in terms of the implementation (we are updating much of our tutorials/documentation this week), but there should be enough there to get you started. In short, you'd need to implement PackageStore and ODataAdapterBase. If you need a reference implementation of either, let us know and we can send it to you.

Wow, that was quick! Thanks!

Not currently; that information is configured at an extension level. We do have a feature on the backlog that would allow for multiple extension configuration profiles, but that's not schedule for a specific release yet. In the mean time, your best bet would be to modify the extension (we can provide source code) to bring these peroperties to the action-level.