It's not a 10% limit. In my view it's a 10% wide open train track. If you are a big organization with a lot of money, 10% is way more than $200. Therefore, if I am your average citizen and I have $200 to spend as a third party, I have to register, but if I have millions of dollars and I want to spend $200, I don't have to register, but the more important thing is where I got that $200. Basically, I can go around and get money from people who don't want their identity exposed through the registration process.
As a libertarian I might say that I don't think we should have that process, but we have it. If we're going to have it, then I think it should apply to everyone. Just because you're rich, you shouldn't be able to get around the requirement of telling the world that you gave a donation to participate in the political process.