That sounds like a really interesting idea! And great work on Outcomes spec! I especially like your changes to the user profile page and agree that it should be of a more pluggable nature.
As for integration with openbadges, there shouldn't be any problems with adding new criteria once your part of implementations is done. I was trying to design criteria for badges to be more or less easy to add by just extending badge_criteria class. I will certainly look into adding Outcomes to the exisiting criteria!