Interesting.
A few questions!
Have you a few examples of practical, real-life purposes?
How would you manage the limit rates?
I had a custom WordPress plugin that allowed WP users to post on Discourse through a single Discourse account (WP comment → Discourse reply). It was barely used, but the post rate limit and the maximum consecutive messages among other things had to be thought about.
So, how do you circumvent these potential issues?
Could you maybe create new Discourse accounts on the fly? 
