With the introduction of person to person Apple Pay this fall and the introduction of Business Chat with Apple Pay next year, will it be possible for business to pay customers using Apple Pay? This seems like the only missing link in the whole Messages/Apple Pay ecosystem.
Is it possible for business to pay customers using Business Chat
I don't believe AP has moved to being allowed/announced plans for invoicing rollout just yet.
Be sure to file a feature request via bug reporter to let them know of your needs, etc.