I don't know if you're going to entice many developers with that combination. What we need is a simple protocol (not an API), maybe JSON/MessagePack based with UDP signaling, that makes it easy to build distributed Twitter-like services, while also reachable by HTTP. The developer experience needs to be easy enough so that a distributed "hello world" service can be built in less than 5 minutes. It needs to come with a cross-platform P2P server component, and client libraries for a few popular languages. Make the barrier to entry so low that any dev can do "apt-get install <fancy-distributed-system>" to get the server/client bits.
The average user doesn't know DNS (username.twitter.com) as well as they do email addresses (username@twitter.com) and URIs (twitter.com/username). If this is going to gain adoption, it needs to prioritize UX familiarity over technical superiority. Everyone has an email address, so use that for identification, but don't clutter people's inboxes by using them to transport or store app data.
Make it super easy to federate with existing walled gardens by providing open-source implementations of server components so Twitter, Facebook, Google, etc. can get up and running quickly.