If I were able to run a program that took all anonymous leads and added an extra field that marked them "international" or "domestic"
In the past, you could enrich anonymous leads via SCs. Now (maybe in the near future for your instance, but you might as well treat it as "now" because it'll break) anonymous leads won't trigger campaigns while they're still anonymous.
IMO reporting on still-anonymous sessions should be done using GA. Marketo can give robust data on the anonymous activities performed by since-converted leads prior to their identification/creation, but it isn't the right place for trending visitors as a whole.
All that said, if there there's a forward-compatible trick, go for it. But I can't think of one offhand.
As a follow up I've never recommended that these reports go to executives. These reports are for territory reps and prospectors.
If you really want to help them see the data, you'll have to prep it for them and send it over in a package. The automation here isn't designed for what they want. GA can do this as well as Tableau if it's setup properly.