I feel that the proposal to regulate device firmware and effectively ban non-vendor firmware is both overbroad and will result in significantly increased security risks faced by the general public (myself included). If the FCC chooses to go forward with this, it should also require and put in place penalties to enforce MANDATORY security updates from vendors within tightly constrained timelines, including to products which the vendors no longer sell or wish to support.
I have used various third-party firmware replacements (generally OpenWRT, occasionally DD-WRT) to replace firmware on routers with known security holes, undoubtedly including some for which patches were years late if ever delivered. I have done this for myself, friends, family and customers.
If the FCC mandates that I may not legally replace the firmware with secure versions unless they come from the equipment vendors without also taking steps to ensure the availability of those security fixes, then the FCC is acting to ensure that the state of network security in the United States is AND WILL REMAIN unacceptably poor.