Is there a reason why all of the above and more cannot be an option?

Nope. That's the thing tho'. Most site implementers are going to have to deal with that headache until there is a proper set of libraries for it.

Are you suggesting it's time to write an abstraction library?

I'm sure that would be useful. How about you implement that.

Maybe it would be something more like blogger has where you select what method you want to sign in with. They have Google, 5 different OpenIDs, name/url, and anonymous.