Hmm. It does sound as if rather than a payment API you’re after a licensing API, e.g. Conditional downloading of content based upon the presence of licenses on the browser’s system.
There’s a difference between adding value and subtracting value.
Using geolocation data to prevent the display of content unlicensed for the viewer’s location, is quite different to making the presentation of information more appropriate and useful in the context of the viewer’s location.
On a related tack one could argue that DRM’s only detractors are politically or ideologically driven. I think that is to misunderstand a far more fundamental reason why DRM cannot work.
As a software engineer I’m not persuaded by ideological arguments as to what is feasible or not. 18th century privileges that require information to remain uncopyable such that its distribution can be commercially licensed are not only ideologically unsound, they are also unsound from a software engineering perspective.
I’m all for facilities that help people exchange money with each other, but I’m always wary of ideological premises based on payment for ‘content’. It’s like proposals for perpetual motion machines. They’re attractive, but there’s a good, non-ideological reason to discount them.
Even so, don’t let me discourage you from explaining more about the payments you suspect HTML5 could facilitate and how it could do so.