Hey Matt and thanks! To answer your questions:

How was this approach to design pitched and subsequently received by stakeholders?

I can’t answer this fully, since I wasn’t part of all the discussions. Overall the company understood that we needed start this work sooner than later and native was the place to start it.

Was creating Airbnb's design system a complete overhaul? -- or injected into a current state of the UI and slowly brought along?

We both approached this bot as design and redesign project. Partly we changed the views and flows drastically and added new features that product teams were already planning to build. This meant that some major flows (home —> search -> booking a listing) were largely re-though, where as some other parts, like messaging followed the previous patterns, and just got update in the style.

Were there any noteworthy hurdles in setting up the teams to work this way? (design+engineering+management alike)

There was definitely lot of coordination we had to do getting everyone using the system. The core team, who designed and built the system, was largely aligned and we could make lot of progress. However, when the started sharing and including more teams to the system and building it, we started to see that communication and documentation came to much more important. This created some confusion that could have avoided with better documentation and communication.

I wrote blog post about this process, which just got published today http://airbnb.design/building-a-visual-language/