What would happen if you used KRL to inject web analytics into various sites using a proxy end point? Is it possible to track multi-site usage with a Kynetx implementation?
This depends on the analytics package you are using. Google Analytics uses a tracking code, rather then domain only, for tracking. They even have a way do your tracking in a way that does not interfere with the site if they also use Google Analytics. Their docs on tracking events on multiple domains might be relevant.
It really comes down to how the tracking engine works. Give it a try, and remember to check and see if sites using the same engine are tracking as well (consult FireBug or Chrome Dev tools to look for the appropriate requests), to be a good neighbor.