FWIW, Swift (the company behind the interbank payment system) has been developing and pushing ISO 20012 as an XML-based long term replacement for their Swift message format, though it's not designed as a replacement for ACH.
For that, there was HBCI years ago (also XML); don't know if it's used much still.
For that, there was HBCI years ago (also XML); don't know if it's used much still.