Making all outgoing links on subsites no follow unless explicitly removed or marked as follow?

Hey folks,

Let me know if you don't think this is a good idea, but I do (considering all of Google's changes in the past few years and years to come)...

What is a good plugin that will take control of all outbound links and make them NO FOLLOW automatically on all subsites (and main site)? Then, each subsite could explicitly mark select domain names as FOLLOW where applicable or needed?

Thought and ideas?