Chip vendors would not give Google the blobs and Google would not waste their own time maintaining firmware for devices they didn't produce. Google might as well produce all the devices themselves which they don't want to do.
What you're basically talking about is bringing all devices under the Nexus branding which will never ever happen. And AOSP wouldn't need to turn into AOCP if they really wanted to do that as they would just have to stop giving google apps and services to vendors.