I've been playing with the idea of a DOM-less Polymer-like library. After few days of hacking this is what I came up with:
https://github.com/arodic/carbon.js
I like Polymer, but I got tired from creating DOM elements and templates for every single piece of encapsulated logic so I made something that allows encapsulation and DOM-like composition in pure JavaScript.
It works with Polymer (with imperative binding only at the moment).
Let me know what you think!