That one's probably easier in a way - you could always just run the GetUsageData for each web object, import that into a data table and filter users with another foreach which looks through the user IDs from the report and creates a subset of the data based on your criteria.
In fact that would be a lot easier than the method I'm currently looking at - I may have to look at doing the same thing myself rather than trying to hammer a custom receiver into the setup.
For quicker building of a reporting app to do it, you could always grab Lightswitch. Currently it's in beta and looks pretty powerful.
Very interested in this, I was just asked today to tell people who uses sharepoint 2010 the most.
I would want to use the basic reports though.
I've got my active directory sorted into year groups.
How would you go about starting this?