Oh, that. It's completely possible to do all of the verification locally, so you don't have to talk to our hosted verifier. We're working on building libraries to make that easier, but we still want to tweak our data formats a little bit before recommending local verification.
In particular, we're watching the IETF's JOSE family of standards pretty closely.
(Persona always prompts you with a completely free-form email input field and routes you to the appropriate provider based on that.)