You're right, it does need some type of ranking. I think the endorsement could be something like that. Instead of having journals endorse it, let specific academics do it. So if Dr. John Doe really likes an article, he can endorse it personally, and put his personal reputation up to bat for it.
And then have an algorithm that sorts based on endorsements, or how trusted the endorsers are ('Do you agree with this endorsement', or how many endorsements they themselves have). Let the authors easily input all the topics they want as tags, making it easy to search as well. And, of course, public comments about what would need to change to get an endorsement, as well as allowing readers to look at all previous versions of an article to see what changed. Basically, let the academics take care of endorsing and topic tagging themselves.
Reviewing every paper by just one to three qualified people is already hard and putting a lot of strain on the system. Trying to solve that by "just have everybody read everything and endorse what they like" is going to break it. Or rather most paper will never be read nor endorsed by a professional. All it would do it turn science into even more of a who like whom.
And then have an algorithm that sorts based on endorsements, or how trusted the endorsers are ('Do you agree with this endorsement', or how many endorsements they themselves have). Let the authors easily input all the topics they want as tags, making it easy to search as well. And, of course, public comments about what would need to change to get an endorsement, as well as allowing readers to look at all previous versions of an article to see what changed. Basically, let the academics take care of endorsing and topic tagging themselves.