Re: I don't much like this idea at all...
From the average consumer's perspective, how are they going to fix this problem? How are they even going to identify the problem?
A lot of botnet nodes are computers or phones running malware. So first thing's first, run malware scans on those. To do that, open your antimalware program and, since the average consumer doesn't run this frequently, update the definitions, except you can't do that, because the internet has been shut off. And it might not work anyway. DDOS attacks are among the most basic ones, which does mean that the kind of people who want to do them often go for a preexisting program to do it. It also means that, if I want to do that and want to go undetected by standard antivirus software, I can write a new one from scratch in about ten minutes, and so can everybody else.
But we've been talking about routers and IoT things which the average homeowner can't do much about. How are they going to identify which among the things they have is doing this, especially if the software has received a relatively basic patch which can be summarized as "if internet went offline, don't DDOS or even contact the servers for several hours so it's a pain to try to get them to find us".
These questions are important. If it's us with an unworkable solution which will cause big problems for people at a whim versus a problem most people never see*, who do you think is going to win? There are two approaches to making this happen globally: get ISPs to do it, or to expound, make ISPs anger their paying users to help people who don't pay them. Good luck. Or it can be mandated by legislation. To get this passed as legislation, we have to be a lot more convincing.
* One problem making this convincing is that DDOS attacks are not things the general public ever feels. The last attack I remember even getting noticed by the public was the attacks on Dyn which was nine years ago, not deemed remarkable then, and quickly forgotten. Ransomware, on the other hand, was the cause of hundreds of attacks which people experienced consequences from, and little has been done about that. It's hard to convince people a problem is a big one with that kind of experience.