It's a cool thought, and it very well be an improvement over today's situation. The major reservation that jumped out at me was that it would hurt fresh content. I'm guessing 100 was a number you just threw out there, but whatever the number, once a site hits that number of quality links, they wouldn't need to produce anything else. Well, at least in terms of link building, they wouldn't need to produce anything else.
Also, different size sites would need different numbers. For example, 100 really high quality DA of 90 and above links would take my site a long time to get, but, Moz, for example, probably already has that. If you decide to make the number really high, 10,000 high quality DA of 90 then it might take Moz awhile to get that, but since neither myself, nor any of my competitors will ever reach number, it's not much of a deterrent for us to get fivver, comment links.