If it has to be adopted, then it has to be based of that all science is supported by tax grants. It simply has to be accepted that all science that receives any government money has to be complete open and that using any portion of the grant to pay for this should be illegal.

Now that nobody (or close to nobody) can publish in Nature some other open access journal will be the number one.

Without the need for printing papers the amount of people actually needed to run a journal drops to a few admin people (research and peer review is still paid for by others) and somebody to keep the website running. This can easily be paid for by a few universities (Harward is sitting on billions and they have an interest in solving this problem).