The functionality and behavior of ZangoDB was tailored specifically for porting a rather complex Mongo-based application to the browser. Syncing was not one of the requirements. However, I am currently working towards adding syncing support, and I am investigating developers' requirements. I will look into how PouchDB handles this. Thank you!
Yes, it is a goal to eventually support syncing. I would like to create a plugin system for it so developers could add syncing support for whatever DBMS they desire. The priority is for MongoDB though.
I am largely impartial to which backend to support. All though MongoDB seems ideal considering that ZangoDB supports it's document based language. Would you, based on your experience and preferences, say that Couchbase should have a higher precedence than Mongo?