This is backwards. Instead of regulating devices they should just enforce the law and penalize those who break it. If you're found to be violating FCC regulations you pay a fine. This is pretty standard stuff. The top-down can't-trust-users thing is such bullshit.
The government lets me own a semi automatic rifle but I can't run non-standard firmware on my router because I might hurt someone.
And of course vendors still need to update the software, so people will just hack that method. Of course you will be violating the DMCA anti-circumvention statue, so it will be a felony. Not to mention this sounds like effectively mandating tivoization which would prevent them from shipping gplv3 code.
Vendors having to come up with an actually secure remote update procedure (rather than ad-hoc secret protocols and "factory passwords")? This is beyond the "greats" like Samsung or LG even.
The government lets me own a semi automatic rifle but I can't run non-standard firmware on my router because I might hurt someone.