Have you tried lptools?
It’s not at all officially associated with the Launchpad project, of course, but it’s got a few nice things that you might want to look at, including:
- a milestone manipulator
- a code review notifier, and
- a milestone to iCal exporter
One of these days, I’d like for there to be an official, awesome Launchpad command-line client. As it is, I’m happy with the world of people making extensions to meet their needs.