There has been discussion on whether they accept other forms of payment[0] (probably lots and lots of times), and supposedly they'll take PRs. Maybe someone should write an external payment API that really just acts like a dummy "blockchain" and works off of human verifications (along with some sort of trust score).
That, or someone could theoretically create a blockchain that did nothing but validate payments on other platforms (I have no idea how it would work but it seems possible), so a payment on the imaginary blockchain would equal a confirmed payment on some payment platform with sufficient API support.
[EDIT]- found another thread[1]
[0]: https://www.reddit.com/r/OpenBazaar/comments/2lddjy/besides_...
[1]: https://www.reddit.com/r/OpenBazaar/comments/531vui/openbaza...