Keep in mind that a blind signature is not very similar to regular signatures. You don't just "slap a sig" on a document when dealing with a blind signature. Rather, a blind signature is more of a mathematical building block used in crypto protocols. It has specific mathematical properties that make it useful in certain anonymity applications. But it's not really very signature-like.

For one thing, the content of what is blindsigned is largely irrelevant. Normally with sigantures we say, be sure you know what you are signing. But with blindsigs that isn't the case. It doesn't matter what you're signing, because you can't see what you're signing. All the semantics have to be in the pure existence of the signature itself, with the content of what is signed largely irrelevant (except for detecting replays and existential forgeries, etc.).

So it's really a different beast, and the difficulties you have faced merging contracts with signatures don't necessarily apply. They could use blindsigs for anonymous cookies or some such thing and it could be a generally simple and straightforward use of the technology.

Of course, if Microsoft is doing financial stuff they will eventually have to address issues of contract semantics, but they won't be related specifically to the blind signatures, rather it will be part of the larger system that uses the blindsigs as one piece.