cool stuff! if zotero already supports webdav as a storage backend, then it should be easy to set up the webfinger->oauth->webdav link. but since zotero is something you install, that might not be so very useful. you might as well store the webdav credentials in the installed client.
what does become interesting is what you say about reusing those bibliography details on other web apps. so for that, it makes sense to us a standardized way to access the webdav storage space, and define a bibliography data scope, with a data format.
this really makes me want to work on app development - if we have a few apps to start with, then we can convince zotero to integrate with them, and then once it integrates with zotero, it becomes attractive for other people to iterate on those first few apps.
i'm pretty busy with OwnCloud, BrowserId, and syncStorage for probably all of August, but could dig into it after that. Maybe there's someone else who wants to pick this up?
Cheers!
Michiel