turns out: no. We're relying on Polymer's resolvePath to turn every component's "./thumbnail.jpg" into a properly pathed URL. We can do that without "customelements" or "elementregistry", but not without a list of registered element propetypes at all - so we can move that list into ceci somehow, but it'd still use the same shim, and would basically just be ElementRegistry's code subsumed by ceci