I think I know how to implement boosting... doing that next.
Once boosting is in there, things will be good enough to go.
I think I'm going to roll out federation slowly so I can catch any catastrophic issues early and before they affect more people.
The easiest way to slowly roll this out will be to only have it available to users with Public blogs (a relatively small group of people). After a couple days of that, anyone will be able to enable federation.