There can be an issue of quality control. There is a huge underworld of outsider intellectual activity, as a trip to vixra.org demonstrates. In certain fields, the eminent researchers receive a steady stream of papers by autodidacts, claiming new breakthroughs, or refutations of orthodoxy. In a field like that, your blind review site will still need some kind of filter; but what could it be?
I was just thinking about how difficult and expensive it is to get a review in journals. How could a blind review of manuscripts, independent of journals look like, would this be relevant for accelerating research progress. A website where you could incrementally improve your idea based on review., this will be the helpful for people who don't particularly have supervisors or associations with institutions. Someone like Ramanujan faced a lot of difficulty in being accepted in the Mathematics community until GH Hardy welcomed him and saw his genius at Cambridge. The use-cases I am thinking of are people who might be out of the academic circle, perhaps at a startup, high-school, sabbatical or a pseudonymous collective like Bourbaki.
Other advantages are , we could be able to find a way to hack the PhD program with this approach, meaning people who are not at colleges could demonstrate their abilities in a particular topic and can be awarded a PhD by an independent institution.