I recently worked on a similar project (with Privy.com), where Mixpanel was one of the external providers we tracked with. Mixpanel handles (AFAIK) an arbitrary

I recently worked on a similar project (with Privy.com), where Mixpanel was one of the external providers we tracked with. Mixpanel handles (AFAIK) an arbitrary number of properties. It was a lot easier than say Google Analytics, where custom dimensions are limited.