Like I said, it would be a difficult problem to solve just as your post shows. But I believe it would be worth the effort. Make the punishment severe for those caught in possession or manufacturing and trafficking to civilians. (speaking of high capacity clips, not guns)
I don't believe millions of law abiding Americans should be punished and have their rights restricted due to the actions of a few. As we've seen in the UK, if it isn't guns it will be knives, trucks, vans, bombs, etc.
In a free society we have to make tradeoffs in exchange for our rights. I'm an AR-15 owner, and I have numerous 30 round magazines. All of my handguns have high capacity magazines. I'm not willing to have to face an intruder or criminal that doesn't care about the law, with only 10rds, and allow him to kill my family because he has high capacity magazines.
There's a plethora of reasons I could add here. Magazine restrictions during the AWB era didn't stop mass shootings, and certain states that have capacity restrictions still have mass shootings. Again, with the freedom we have in this country, if someone is intent on doing harm, they will be able to do so, and clearly the legality of what they are doing doesn't matter to them.
Because of our porous borders, the millions of high capacity magazines already in circulation, the ability to 3D print or even just fab your own magazines with access to readily available equipment, I'd don't see how any plan would work any better than just an outright gun ban.
There is no silver bullet. There are a variety of things we can do with the mental growth system, reviewing what kind of crimes or police encounters can cause you to face firearm restrictions, and better reporting, but there isn't a one size fits all approach that will make people stop killing each other.
I think there's a similar issue with drug addiction and the war on drugs. Obviously, our current results with gun violence and with drug addiction are both very dissatisfying. But I don't think there are easy answers.