When I've sketched out designs for similar systems, I've dealt with that problem by having it acceptable to hire reviewers. Me expectation is that high karma reviewers would be in high enough demand that they could make a living as reviewers.

I'd also expect that there would be science writers who would serve as reviewers to get the earliest possible access to research that might be interesting to write articles about. (I'm assuming most researchers would want to get at least some reviewer feedback before putting their paper out on some public site).