> you could provide a central service where people would buy credit to be used on many sites.
That central service is going to lock out many countries and regions as well as lots of people (minor, unbanked, poor, etc.) in non-locked out countries and regions. Payment is frigging hard especially on the international scale. This is every bit against freedom of information and strictly worse than Cloudflare.
Having said that, you could provide a central service where people would buy credit to be used on many sites. So the micropay isn't the problem.