How about doing a scraping of e.g. 10k Google Scholar profiles with more than ~10 publications to get the domains of their verified email addresses? Then you ha

How about doing a scraping of e.g. 10k Google Scholar profiles with more than ~10 publications to get the domains of their verified email addresses? Then you have a much broader whitelist than just *.edu. Or you can crowdsource this, say I want to register as john.doe@instituteoptique.fr; in the registration form simply require me to give a link to someone's Google Scholar profile with an email address from the same domain. It should also be noted that e.g. on Figshare, anyone can upload any PDF and get a DOI for it.