Yeah it is hard to understand what you are trying to accomplish and what is your workflow for working with data.
Object data you have loaded from source (server etc) you supply to can.Map constructor to get structure and functionality you want to work with. Also you can define (override default) serialization rules (methods) that will bring needed raw (POJS) structure "back" for you to store it in local db, to send on server, whatever.
Look at define plugin http://canjs.com/docs/can.Map.prototype.define.html it allows you elegantly set rules for converting object to can.Map and serialization rules as well.