Doesn't make sense if the "owner" abandoned the project and N goes to infinity. Then we have the same problem. If you're producing open source software, you have ALL the right in the world to abandon a project for arbitrarily large N days. If you don't want vulnerabilities, don't run code from untrusted sources, simple as that. This whole discussion is a farce. The reason open source comes with a license attached to it is for situations like this.
It makes a lot of sense if you realize many people who don't actively spend time maintaining something might still have a desire to spend 10 seconds glancing at others' changes to make sure their own rears don't get burned.
Sure, but this fails if they don't want to spend that 10 seconds, which they totally are allowed to. Since there are hundreds of packages in your dep tree and it takes only one attacker for all your bitcoins to be stolen, your scheme is not enough.