Lars,
This stuff sounds great. It reminds me that something we've built into the MACS version of the APM would probably be of interest to you: We added an XML based package uploader/downloader a year or so ago in the apm, this lets people automatically download recent packages right from the APM interface.
We added space for OpenACS packages at the developer site, intending for it to be available for everybody to use, but we didn't spend any effort convincing people it would be worth doing, so the OpenACS package area is empty right now. (easily remedied with some uploads, though.)
However, we use this for all of our sites right now, if we need to download / upgrade a package, we just go the apm, click "load a package from the web repository", and select from a list. The rest is automatic. This seems like it might work nicely with what you're doing. I believe the code is in the module at the following link, feel free to use it.
Acs-admin package download
